Superman/Batman: Apocalypse
Some great fighting scenes. Definitely the best superhero fights outside of comics. Um, plus a cute Supergirl shopping montage.
And if have no intention of seeing the movie, can at least watch a couple of the fights:
http://www.youtube.com/watch?v=1ID4c4zUgow
http://www.youtube.com/watch?v=PBLpFDEmJUE