Transformers, from 2007. I used to like it as a guilty pleasure, but now that I'm older, I just see how awful it really is. I still enjoy watching these big robots punch eachother, but better movies have come along since doing similar stuff (not the sequels, those were dead on arrival to me), and the characters and comedy are just so painful to sit through that I can't bring myself to like it anymore.
I also used to like Cars, but I've started watching more movies since, and I've come to realize just how formulaic it is. The story and characters are completely auto-pilot, with Paul Newman being the only good thing in it. The animation is decent, and even though it's not awful, it is a dumb idea. I should also mention, I refuse to watch the second one, as it doesn't have the only thing I still like about the first one (Paul Newman died shortly after the first one) and from what I hear, it's shit anyway, so why bother.