Not the genre itself, but more the quality of these "blockbuster" superhero movies. They all had the same overacting, mind-numbing special effects, and A-listers at the helm, often miscast. (See: Edward Norton in The Incredible Hulk.) They became tiresome and predictable.
Maybe that's why I so thoroughly enjoyed The Avengers. Yes, it has your traditional "save the world" credo, the action-hero one-liners, the whole bit, but there's something very genuine about this movie. While I give most of the credit to director Joss Whedon (who knows how to create a project from beginning to end), his team of writers and the work of Marvel/the incredible Stan Lee, I have to bestow kudos on the ensemble of actors who pull it all together.
Some hit their character's mark better than others, though I will say that they're all appealing in their own right. But who lights up the screen the most? Who do we really end up caring about? Here, in a very particular order, are my rankings for the Avengers.
Warning: There may be some SPOILERS.