That's a bit of a bugbear for me. I enjoyed Incredible Hulk. I'd rate it better than Thor to be honest, which is my least favourite of all the Marvel Studios films. Still damn good though, don't get me wrong.
Hmm when you put it like that it might struggle to top HP. It'll come very, very close though. Although, the HP series went careening spectacularly off the rails* in the last two or three films so The Avengers with its combination of hype and alleged quality might surpass it yet.