I remember watching Iron Man and thinking to myself, 'Man, they corrected all the mistakes they made with Hulk!' They started off the movie with rock. Stuff blew up. Then they rewound a bit to tell some story - it was great. Hell, my biggest complaint of the movie was that Iron Man was gimped during the finale and couldn't actually do anything cool. The rest of it was fabulous.
Upstaged only by The Dark Knight, which was simply an epic movie. Batman Begins was certainly an upgrade from the old series of Batman movies, which heralded from the days of the gimmick action film: see the original Batman movies, or the old James Bond movies. Both the Bond and Batman series have benefited from this removal (mostly) of gimmicks: no longer does Batman have carousel reversal spray, nor does Bond get introduced at the beginning of each movie with a myriad of unlikely gadgets that will inevitably find one crucial use somewhere in the movie.
The X-Men movies, on the other hand, grew more and more gimmicky. The third movie was like a cinematic trading card game, with Magneto walking around asking mutants 'What do you do? And you?' Even the last fight was like a Pokemon battle. 'I choose you, Pyro!' I might have to give the Wolverine movie another watch, because most folk seem to like it and I thought it was shit - the plot was all kinds of convoluted, and story strands from the previous movies were re-written in ways that don't fit.
And then Spider-man...well. I much enjoyed the first two movies. And then the third happened. Now, I grew up on Spider-man comics. And Venom was pretty much my all-time favorite character, period. So when they &^%$ed him up, I was done with the movie. To make matters worse, they picked Sandman, one of the least believable villains available (Green Goblin? Genetic modification, okay. Doc Ock? Again, within the realm of believability, even if the fusion science isn't accurate. But sentient sand? That can fly?). Fail.
So, to summarize: the new Batman movies (because of The Dark Knight), Ironman, Spider-man, and X-men, in that order.