There is a surprising lack of Safeco mentions. It is gorgeous, and on a long August evening, its a great place to watch a game. Probably my favorite.
I live in Denver now, and Coors is ok, but it still behind Safeco in my book. I grew up a Cubs fan, and Wrigley, while it has its charms, is also kind of disgusting.
Fenway is weird. Its gorgeous when you are on top, but underneath it looks and feels like a crappy AA stadium. I actually have little desire to go back.
I haven't been to Camden in years, but I remember it being beautiful.
Petco is also great, but in some ways Petco is like a vacation; it almost feels fake. The fans aren't too intense about the game and there are dog parks in the outfield.