The first Iron Man was the perfect superhero movie-- full of action, convincing plot elements, amazing effects, and fantastic comic book action. I would say that only the Dark Knight was better.
And so, with this thought, all Marvel geeks (such as myself) went to see the long-anticipated sequel. I would say that it didn't live up to the hype, but the inflated expectations certainly lowered people's thoughts on the film. This was a great superhero movie, by all accounts, but certainly nowhere near the first. The plotlines were far less coherent, and the suspense and action were, frankly, not as interesting.