Wow, that's one heck of a revived thread...
Since we're going with overrated, and not "bad", I'd say Dark Knight.
Good movie, but can't help but feel public reaction was buoyed by the tragedy surrounding its release. Whether Ledger is the best Joker ever is a matter of personal choice; there's a good argument for the others like Nicholson and Hamil.
I know many will disagree, but I think Guardians of the Galaxy is pretty overrated too. Again, fun, good movie, but the way people are gushing over it seems a little over the top.
And lastly, and worst, Hunger Games/Lion King. It's hard to justify that much critical acclaim for blatant rip-offs of Japanese masterpieces, especially when the writers don't have the integrity to admit it.