Here are my rankings for every stadium that I've seen.  It's purely subjective, but I based these rankings on architecture, atmosphere, how well they fit within the city they are in, and overall history...

(Updated 7/24/2015)

1. PNC Park (Pittsburgh, PA)

2. PETCO Park (San Diego, CA)

3. Busch Stadium III (St. Louis, MO)

4. Busch Stadium II (St. Louis, MO)

5. Wrigley Field (Chicago, IL)

6. Target Field (Minneapolis, MN)

7. Kauffman Stadium (Kansas City, MO)

8. Minute Maid Park (Houston, TX)

9. Coors Field (Denver, CO)

10. Great American Ballpark (Cincinnati, OH)

11. Progressive Field (Cleveland, OH)

12. Globe Life Park (Arlington, TX)

13. Miller Park (Milwaukee, WI)

14. Dodger Stadium (Los Angeles, CA)

15. Comerica Park (Detroit, MI)

16. US Cellular Field (Chicago, IL)

17. Chase Field (Phoenix, AZ)

18. Turner Field (Atlanta, GA)

19. Angel Stadium (Anaheim, CA)

20. Rogers Centre (Toronto, ON)

21. Metrodome (Minneapolis, MN)

PNC Park: basically the perfect ballpark. I love how it sits right on the river and you can take a water taxi to the game. The view of the Pittsburgh skyline and Clemente bridge is unrivaled in all of baseball. The overall architecture is amazing. It feels like no matter where you go in the ballpark, you discover something new. Just a perfect, beautiful, intimate ballpark

Petco Park: Not the greatest atmosphere in baseball, but I love the structure. I love how they integrated the Western Metal building into the ballpark. It just works San Diego and the Gaslamp district that it's in. Literally, it screams San Diego.

Busch III: I may be a bit biased, but I love Busch III. Some call it cookie cutter in terms of new ballparks and criticize the fact that it doesn't have a 360 degree open concourse, but I think it's one of the best ballparks in baseball. It's a hybrid really. The Cardinals have done one of the best jobs in baseball integrating their history into their ballpark. From the statues out front, the Stan Musial entrance, and the scoreboards that were brought over from old Busch Stadium, it just full of the rich tradition of Cardinals baseball. The architecture is a nod to the buildings found in downtown St. Louis, and the view of the the arch and the downtown skyline nearly matches that of Pittsburgh. It's really a hybrid, in my opinion. It's like the Cardinals took what was great bout Sportsmans Park, Busch Stadium II, and combined those things with the modern amenities of many of the other retro ballparks built in the last 20 years.

Busch II: Yes, it was a cookie cutter park; however, with the 1996 renovations, it was easily the best of the cookie cutter big bowl stadiums. It's an experience that is now lost in Major League Baseball. Every once in a while, I miss the massiveness of the ballpark, especially when it was full. I remember just how loud it could be. Also, the arches around the top of the park were a truly distinctive feature.

Wrigley Field: Not alot to say about Wrigley that hasn't been said 1,000 times before. There's something to be said for experiencing baseball the way it was 100 years ago, more or less. Yes, the concourses are cramped, and it lacks many modern amenities, but that's a refreshing change of pace. Going to a game at Wrigley is an experience, a party, as much as a sporting event. The greatness of Wrigley isn't as much found in the ballpark itself, it's the neighborhood, it's the history.

Target Field: Anything was better than the Metrodome, but Minneapolis succeeded in building a distinct and refreshing ballpark in the era where red brick dominates alot of the facilities built in the last 20 years. It has an almost ultra modern and sleek feel to it. It is integrated wonderfully into downtown Minneapolis. My only knock on the place is that it seemed like the upper deck concourses were extremely cramped and strangely small for a modern facility like this.

Kauffman Stadium: I'm typically not a fan of places that aren't well integrated into the city they are in, and that can certainly be said about Kauffman; however, "The K" still manages to be a great ballpark. Even though it's far removed from Kansas City, it takes that negative and turns it into a positive with the best tailgating experience in all of Major League Baseball. Built in an era of cookie cutter multi use bowl stadiums, Kauffman found a way to be interesting in an era of architectural minimalism. No matter how many times I go to Kauffman, I'm impressed by the fountains. The recent renovations have managed to make it even nicer and it rivals many of the brand new ballparks built in the last 15-20 years.

Minute Maid Park:  This park ranks much higher than the other retractable roof domes I've visited.  It resonated more with me because I can't help but love the quirks of this facility.  It's an extremely photogenic ballpark and is an incredibly memorable place to visit.  I loved the train, the hill (which is sadly going away), the views of the city through the windows, and the way it's integrated with the old train station.  It feels like a baseball playground and I loved every minute of my visit.  One of my greatest ballpark visits overall.

Coors Field: One of the early "retro" ballparks build, and still one of the nicest. The Rockies may not have a ton of history and tradition or a rabid fanbase, but they have a gem of a ballpark. It's unfortunate that it doesn't have views of downtown Denver from inside the ballpark, but Lo-Do is a fun environment, and the ballpark in and of itself is beautiful.

Great American Ballpark:  I was more impressed with GABP than I expected to be.  Much more.  The facility has great sight lines.  I love the way they build the Reds Hall of Fame as part of the complex and the Reds Hall of Fame is impressive in and of itself.  I also love how the ballpark complex is integrated into the riverfront.  The entertainment district next to the ballpark is also top notch.  The facility itself is meticulously clean and well kept (which is a factor I've used to downgrade ballparks like Cleveland and Detroit).  The only complaint I have is that the ballpark doesn't do enough to integrate the impressive sights outside of the ballpark.  Sitting in GABP, you don't really realize you're on the river and can't see the boats passing by like you can in Pittsburgh or the interesting bluffs on the Kentucky side.  I kind of wish that the Reds would remove the top 10 or so rows from the right field seating to open up the views and make the experience more distinct.  Still, a top notch facility.

Progressive Field: I visited Cleveland in 2011, and came away expecting more. Jacobs Field had the reputation as one of the great ballparks in baseball for many years; however, when I visited, it just seemed like the place is in desperate need of a facelift. It doesn't seem to be aging well. Much of the architecture screams early 90's and it just seemed like it isn't being kept up very well. I noticed alot of decay and crumbling in the concrete. The view of downtown Cleveland is still very impressive and I liked the way it's seamlessly connected with the basketball arena next door. It has a very unique layout with the high wall in left field that is actually on street level. I'm not saying I dislike Progressive Field, but I just expected more. Also, the fact that the Indians were drawing less than 20k and were in first place when I was there was disappointing.

Globe Life Park:  I didn't enjoy this ballpark as much as I'd hoped.  The area where it's located detracts from the experience a bit.  I typically enjoy ballparks that are integrated into downtown cityscapes.  It adds to the overall flavor of the experience.  It's a serviceable ballpark.  It's massive, but it seems like some of the architectural quirks are a there just to cover up the overall blandness of the area.  It's also another facility that was built in the 90's that's starting to feel like it needs a renovation.

Miller Park: Miller Park isn't a bad place, but it feels like less of a ballpark and more of an arena or maybe an airplane hanger. I was lucky enough to see a game with the roof open and one where it was closed. It's a totally different experience when the roof is open. I prefer it that way. At least some natural light gets in and you somewhat forget how massive of a place it is. Also, the fact that is so far removed from downtown Milwaukee is disappointing, but like KC, they are somewhat able to make up for it with a good tailgating experience. Overall, I'm just not a fan of facilities as massive as Miller Park.

Dodger Stadium: In some ways I feel like I can't truly evaluate Dodger Stadium. I made the mistake of sitting in the bleachers for my only game in this ballpark. I didn't realize at the time that I would be cut off from exploring the rest of the ballpark. This was back in 2000. I can only assume that it's still the same today. It's a well maintained, truly historic ballpark, but I don't think I got a chance to experience everything Dodger Stadium had to offer and it was very annoying that I was confined to the bleachers.

Comerica Park:  I like the view of the Detroit skyline from the ballpark.  It is the signature feature of Comerica Park.  I also love the tiger statues all around the exterior of the stadium.  It is a well laid out ballpark overall.  However, there were some issues that prevented Comerica from being rated higher.  I visited Comerica the same weekend I went to Great American Ballpark, and I couldn't help but notice how much more well maintained GABP was.  Comerica Park is less than 15 years old, and only 3 years older than GABP.  While I found GABP meticulously maintained, Comerica was not.  Honestly, it looked a good 15 years older than GABP and I found it kind of sad.  There were visible signs of decay already including missing bricks, rust, etc.  I had similar thoughts about Progressive Field in Cleveland.  Comerica was opened in 2000, but it already looks like it needs substantial renovations.  Also, it's simply the reality of visiting Detroit, but the area surrounding Comerica doesn't offer the type of outside entertainment options that you'd find in cities like San Diego or Cincinnati.  It's a nice ballpark, but it's already showing its age.

US Cellular Field: I first attended a game on the South Side of Chicago in 2003. I did not leave with a high opinion of the ballpark at that time. In fact, I rated it as one of the worst I had seen. The upper deck was incredibly steep. It would honestly make you dizzy to sit near the top of the upper deck. Again, US Cellular, like sitting in the bleachers of Dodger Stadium, confines people that have upper deck tickets to the upper deck only which is a terrible decision. I went back to US Cellular in 2012 and my feelings on the place have softened a bit. It's still a massive monolith of a stadium. When compared to places like PNC Park, it really can't be called a ballpark. They still confine people to the upper deck, but at least the renovations shaved off a good 10 rows of terrible seats from the upper deck. Also, it seems that the renovations made strides to incorporate the history of the White Sox franchise into the park. I like the statues in the outfield. US Cellular is still not in a very good area, but it seems like the neighborhood is better now than it was in 2003, but there's still very little to do around US Cellular. All things said, it's a better place to watch a game today than 10 years ago, but it's still not in the upper echelon of MLB Ballparks.

Chase Field:  Chase feels quite a bit like Miller Park, but I'd say it's not quite as fully realized of an experience.  I rate Chase lower than Miller Park due to the outside of the facility not being as architecturally interesting.  I appreciate that Chase is downtown, but Miller has a great tailgating atmosphere going for it and that is missing here.  Overall, it's a pretty sterile environment and it tends to feel like an airplane hangar on the inside which is a typical complaint about the late 90's-early 00's retractable roof stadiums.  Downtown Phoenix is a fun place and I love the city, but Chase seems so closed off from all of that with the roof closed.  I imagine that it's a totally different experience with the roof open, but it's so rare that the ballpark is experienced that way.  I do give them high marks.  As they often point out, they are the friendliest stadium that I've ever attended.  All of the employees were extremely nice and helpful.  The prices of many concession items were extremely reasonable.  A hot dog and pop corn could be purchased for $1.50 each.  You don't see that at most MLB stadiums.  It was great to see, but while the experience is fan friendly, it still tends to be a bit bland.

Angel Stadium: To me, Angel Stadium is kind of like Frankenstein's Monster. It's been built, torn down, rebuilt, and renovated so many times it's a bit of a strange place. It has some history, it's actually one of the older ballparks in baseball at this point. I suppose it fits in with the area that it's in, but the Disney renovations of the 1990's make you feel like it's an extension of the theme park. It just doesn't work for me. The area where the ballpark sits is rather devoid of anything outside of the ballpark. If there was anything else around there, I certainly didn't find it. It's a comfortable place, but it just didn't have much else going for it.

Turner Field:  Turner Field is a nice ballpark.  I wouldn't consider it in the upper echelon in Major League Baseball by any means, but it's nice, clean, and well kept (moreso than Progressive Field in Cleveland).  It also earns points for the historical fact that the 1996 Olympics were held there.  I sat in the Club level and the accomodations were very nice.  I also like the fact that they maintained much of the footprint of Fulton County Stadium and the spot where Hank Aarons record breaking home run ball fell.  The view from inside the park is somewhat generic.  While other ballparks like Busch and Progressive integrate seemlessly into the cityscape and offer amazing views of downtown, Turner Field is isolated in an area somewhat remote from downtown and with the seats/offices in left field as well as the huge jumbotron, it feels incredibly closed off from the city around it.  Honestly, unless you sit in the upper deck, it appears you can't see much of anything around the city and that's a shame.  It's a nice facility, but I prefer ballparks that give you a taste of local scenery beyond the ballpark.

Rogers Centre: Toronto built their facility about 5 years too soon. It felt like a trip back in time to me to an extent when I visited Rogers Centre in 2006. So much artificial turf and concrete makes you feel like you're watching a game back in the 80's which was certainly not one of the prettier times in the games history. They've tried to make it a high tech playground with alot of video boards, but it doesn't compensate for the massive amounts of concrete and the overall size of the facility.

Metrodome: I'm so happy for the people of Minneapolis that they have Target Field. When it comes to the Metrodome, it pretty much goes along with the old adage, "if you can't say something nice, don't say anything at all." It's too bad the fans in Minneapolis had to suffer through such a terrible facility for so long. The baggie in center field, seats that faced away from home plate, a stark white ceiling, and a pressurized building that literally sucked you into it. I don't know who ever thought that was a good idea, but I'm glad it's gone.