Nolan's Batman, followed by Spiderman.
The X-Men movies were probably the worst superhero movies I've seen.
Come to think of it, probably some of the worst movies I've seen full stop. (Though for some reason, I enjoyed Origins: Wolverine)
The only reason I'd see First Class is to see Jennifer Lawrence's (main actress from The Hunger Games) performance as Mystique, which I've heard is good.
I also enjoyed Iron Man, Thor, and The Incredible Hulk.