The big movies that have surprised me are the Super Hero/Comic Book ones.
Namely, Spider Man and the X-Men series. I like(d) the films when I saw them... But their sequels completely won me over as far as these being "legit" franchises that are worth my time and I will make it a point now to go and see them when they are in the theaters and not just wait for DVD because I end up regretting it.
As far as disappointments... Garden State.
I had heard it was this amazing film and it has such a great cast (and it does)... But ultimately, the movie left me numb and empty.
I admit, I am probably not the movie's main target demographic (teens; early20s), but I usually like any film that deals with emotional turmoil and drama no matter whom the movie is aimed at, I.E. Mean Girls... But this one I felt was just more hype than substance and or I just can't relate to it because I am not 18, any more.
Garden State is a good movie, but I think its been hyped up into this paragon of Generation Y just so they have something to claim as theirs and identify with.