Parks I've been to in order of enjoyment:
1. Old Tiger Stadium...just a classic, not the prettiest joint, and there was a good chance you would come back to a tire-less car, but what a wonderful place to watch a game...I thought I saw Al Kaline in the Tigers dugout, there was that much of a historic feel to it.
2. Petco Park...just a beautiful stadium in one of the most beautiful areas of the U.S. not a bad seat in the place...if only the Padre brand of baseball was more fun to watch. (At least, I saw my Reds destroy them)
3. GABP...I miss it terribly, loved sitting out in the moon deck.
4 a. Angel Stadium....took my future wife there on one of our first dates, they played Oakland and I couldn't even tell you what the final score was.
BUT, I do know it's a nice place to watch a ballgame, and I actually enjoy the "water feature" in the outfield that goes off for Angel home runs.
4 b. Coors Field ... Really liked the feel of this one as it was one of the "retro" stadiums and I saw a game the year after it was built. Enjoyed it quite a bit.
5. US Cellular ... The ballpark is largely unremarkable, but Chicago is a great town, and really this is a fun place to watch a game. Take the subway, makes it a lot easier.
6 a. Dodger Stadium ... This one was disappointing for me. Someone else said they thought it carried its age well...they must not have sat in the outfield bleachers...it's a pretty run down area. Could use a face lift. Food was just "ok" and mega expensive.
6 b. Riverfront ... It only gets this high because I'm a lifer Reds fan. I hate astroturf, so the original Riverfront was blech for me. When they did the mini renovation on it, and put in turf and opened up that section of the stadium in left it felt a LOT more like a ballfield instead of a multipurpose stadium.
Honorable mention: Fifth Third Field (home of the Dayton Dragons) ... yes, it's not a major league stadium, but it's such a great place to watch a ballgame that it had to make the list. The front office really goes out of its way to make families feel welcome and have a great time. Plus the stadium is beautiful! Set the all time single season record for consecutive sellouts and still counting.