It doesn't quite knock off Superman, Dark Knight, or Spiderman 2 but it definitely belongs with them. It also one of the most pure comic book movies I have seen in the superhero genre. The action is good, the characterizations are spot on and consistent with the preceding movies. Best off all everybody gets a chance to shine. It has funny moments, amazingly the Hulk has the best line, moments that make you go woah! and serious moments. I don't think the 3D adds anything so you won't lose out by seeing it in 2D.
I think this will be an important movie for the superhero genre in that it brought some things that were missing in previous films. While this being the climax of Marvel's introduction comic book style continuity is important, it also much more action oriented than previous films. The superheroes feel more like well superheroes.
Go see it.