I don't think it was a bad movie. I think that after the sheer awesomeness that was Iron Man, knowing that this one is also a tie-in to the coming Avengers movie, I was just expecting a little more. Iron Man set the bar pretty high.
There were some very cool moments in it, though. I was cool to see Hulk get out his famous line - "Hulk smaaaaaash!" And the comical scene with the purple stretchy pants was cool. And there was the foreshadowing of Thor. Did anyone else catch that? I didn't really notice it right away, but then later, after I got home and went over it in my head, it dawned on me. It was definitely an "Ohhhhhh" moment!
"Human tales? But human don't have tails, they have big, big bottoms that they wear with bad shorts, and walk around going, 'Hi, Helen!'" -- Batty (Robin Williams), in Fern Gully