Red Faction: Guerilla. My freaking god was that game EMPTY. The world had almost nothing in it. Why weren't their huge cities to rampage through? Tall buildings to pick apart? Plus, you died really easily, and your AI companions had some of the worst AI I've ever seen in a game, AND you could barley carry any ammo. 3 clips at a time for your assault rifle? What am I supposed to do with that, give my enemy a back massage?
I also felt that Red Dead: Redemption didn't quite live up to the hype. Don't get me wrong, it's a great game and worth $60, but the way people talk about it, you think it would be the best game of all time, which it isn't.
As I'm sure many people here know by now, I also didn't think Half Life 2 was worth the hype. I mean, it was fun, but the level design was so bad that I spent half the game looking for what path I was supposed to take. Luckily episode 1 and 2 were much better.
Oblivion was the most overhyped. That game was painful to play though. The combat was bad, the story was bad, the main quest was bad, the voice acting was bad, the animations were clumsy, the leveling system was atrocious, the open world was bland, and overall, it didn't come anywhere near to the hype. Despite what people say, I still say Fallout 3 is miles better. On the bright side, the side quests were a LOT of fun and very imaginative, especially the guilds. Too bad the rest of the game couldn't have been that fun.
Oh, and Fable 2. Now, I love the Fable series, and I really liked this game. I still hold it up as having one of the best combat systems ever, but it still didn't live up to the hype. Barley ANY side quests, a short-ish main quest, barley any variation in weapons and combat styles, a huge closet of cloths with maybe 10% of them being stuff you would ever consider wearing, and the world. Now, I never had a problem with Fable 1's linear-open world. When Molyneux announced that Fable 2 would have "If you can see it, you can go to it", I was rather excited, only to find that Fable 2 only had slightly more freedom of travel than Fable 1. Again, I didn't have much of a problem with that, it was fine in the first game and fine here, but it was a blatant lie by Peter Molyneux. You want a game where "If you see it, you can go to it"? Play Fallout 3.