Just to clarify, I didn't say i disliked the Half-Life series, just that it is over-rated.  I tend to enjoy them.  Single-player great, multi-player a little disappointing.

FFVII overrated by fans not reviewers
MGS2 I should have stopped here, who cares if I missed MGS3..I'm not specially fond of 4 either.
Kingdom Hearts gameplay is very boring, I decided to read the story off some sites, YES READ!
FF12 and FF10-2 overrated by reviews much better RPG games out there
GT3-5, I loved GT1 skipped 2 and decided to play 3, I quickly learned that I no longer like this franchise
Rockband - Above 90 score? WTF, if this a 90 game GH should be 90 and so should DDR and the rest.

Honestly I could go on.

Final Fantasy VII by far. I have never seen such a below par game get heaped with such praise. I was a huge Final Fantasy fanboy when the game was released. I played through it twice trying convince myself to like the game but I had to face the awful truth. Final Fantasy VII was atrocious. If Final Fantasy VII didn't have Final Fantasy in the title I would have never forced myself to finish the game. The story was terrible, the gameplay was dumbed down, the graphics were only good during battle, and the sound was quality was poor. Throw in an emo protagonist along with the worst antagonist in series and you get the most imperfect storm in my gaming life. The worst part was that I couldn't say it was some crappy side game like I could with Mystic Quest.

There are other games that I feel are overrated. Halo 1, GTAIV, Majora's Mask, Oblivion and MGSIV all come to mind. The difference between those titles and FFVII is that those games are good games that overrated. FFVII was/is a D- game with AAA reviews.

Edit: Acevil, reviewers universally called FFVII the best RPG of all time and gave the game 9s and 10s across the board.