While I admit to enjoying Iron Man (haven't seen #3 yet), I recently saw the Avengers and I couldn't believe that movie actually became one of the biggest ever. It was thoroughly plain in every way. I can't understand how it made such huge numbers, I really can't.
I don't understand it either, IM1 is about the only one I really liked. TA was just okay, the way people hyped it to me it was just.....ergh.
I do enjoy Nolan's Batman movies a lot however.