Ok here it comes people, brace yourselves...
Planescape Torment
Yeah, seriously. I just never figured out what it is that people see in this game and God knows I've tried. It is just... uninteresting, and the leveling system is so confusing. Generally, when I level up my characters in a RPG, I'd like to know how each stats affects my character so I can develop them the way I want to. In Torment I had no idea how to get myself, for example, a mage-type character and how to expand his magical abilities. And what's with the immortal main character? "Oh no I just died!!! Oh wait a second, nevermind..." But I must confess that I never really got into this game despite the time and effort I sacrificed for it, so maybe I've misjudged something. On the other hand, I never found the game entertaining enough to keep on playing, so that does tell something, doesn't it? Oh well, I guess you just can't like 'em all. Now go ahead and crucify me to the Tree of Woe.
Ok, some other games then:
Half-life series
While they are all great games, they're not the ultimate "ZOMG LiKE bEst games EVAH!!11!!" to me.
Halo series
I'm a die-hard Halo fan but I do acknowledge the fact that the games, while I find them very entertaining, aren't really that groundbreaking in any way and are massively overhyped due to their popularity.
Bioshock
Another of the rather obvious choices. It's a decent shooter with nice visuals but gets oh so boooring, and the story isn't all that ingenious, regardless of what the critics say.
Morrowind
While being my favourite game ever made, some folks just go too far with their praise for it. It is in many ways a flawed game, after all, although that has never kept me from enjoying it.
Oblivion
The number one game of pretty much every critic and casual gamer back when it was released. I never thought it to be more than average, and I even hated the supposedly stunning visuals. Everything just shone like a nuclear blast and the characters looked as if they were made of rubber.
Call of Duty series
Can't really say I've played too many of them but from what I've seen I'm not convinced they're worth the hype. When you think about it, a game series that has received as much hype as COD simply can't be worth it, right? I mean, the games might be cool and entertaining and all, but to match the amount of praise they've received they'd have to be out of this world...
Coming in summer 2012: Call of Duty 9: Out of this World Warfare
Oh well...