Final Fantasy VII. Significantly overrated and it "borrowed" too liberally from Phantasy Star II. Yes, I'm still bitter.
Any GTA after Vice City, which IMO, was the pinnacle of that franchise. GTA III was the revolution; Vice was the opus. IV was a good offering, but time has shown that it was just a modernized version of GTA III. No one reveres IV as they do III.
I don't know if I'd call the CoD series overrated, because I don't know any remotely serious gamer that considers them more than just disposable FPS multi-player fun.
Uncharted series - though fun, I find these to be a little irritating. I feel like all I do is jump from hidden ledge to hidden ledge and then get stuck in a far-too-long gun fight. The plot, while always fun, is just ridiculous at times.