Easy choices right here.
Call of Duty Modern Warfail 2. A huge step back, not worthy to mention all the "not balanced for" issues when the whole games was as balanced as a drunken monkey trying to do a stall with a BMX on top of a stake. It brought K/D whoring to the masses and this in effect killed FPS gaming as people no longer really cared about winning, but their e-peen and K/D (not that you would have any use for stats in CoD, because unlike BF there is no place or retrieve them, and have them constantly updated automatically outside the game and show them off as your signature on the forums)
Call of Duty Black Ops, although I must admit it's lightyears ahead of MW2, it still sucks because gained massive hype for nothing
Halo 3 (a.k.a. "My first FPS" for just about half the Xbox users, also, FPS belong to the PC, it's just painful to watch someone turning around playing a FPS on a console)
Halo Reach (not as bad as Halo 3, there were improvements, but it's still bad)
Red Dead Redemption - I don't know, I just don't like how every 12 year old Xbox user suddenly became a western fan; and it's also console exclusive, thought it wouldn't have been better than GTA 4 and it's share of obvious console port characteristics.
Grand Theft Auto 4 - I have the disagree with the person that said vehicle handling got worse. Vehicles improved tenfold at that chapter. It just screams console port.
Forza 3, just because it's not worth playing racing games because every second person is trying to shove you into a wall, and let's not mention how the VW group bribed T10 to make every single VW, Audi, Seat whatever go 2 times faster than in real life.
GT5 - Now this is even worse than Forza 3. Six years waiting for what ?
Vietcong 2 - This is just the "Breakin 2 : Electric Boogaloo" of the game world. First one was decent, but then this comes out and it gets over 9000x worse.
Uncharted series - I fail to see what's so fun and immersive. the whole level design is a pipe with two bends in it and it requires about as many skills to play as it takes to butter a slice of bread.
Battlefield Bad Company 2. Slightly. I am a Battlefield fan myself, but for God's sake abandon the singleplayer. Or at least they could've kept it less serious like in the first game. I don't know what's with the misconception that a FPS has to be serious. Basically : MP is where it's at, and if they're gonna keep doing the BC series, they might as well keep the SP story fun. Multiplayer...hell, I'm still lovin' it.
Medal of Honor 2010. It didn't live up to it's hype. Yes, I enjoyed it. I loved it but it could've been a lot better.
Crysis. OK, let's be honest, do people buy it nowadays for the cheap gameplay or just to test their PCs, this being nothing more than an interactive graphics benchmarking program.
Starcraft 2. Worse than GT5...I can't even remember how many years for...basically a graphics update. Still the same pissed off Koreans. S.S.D.D. (or should put up a "Y" instead of that last "D")
For next decade I hope that this list will not include Battlefield 3, Mass Effect 3 or Red orchestra 2 : Heroes of Stalingrad (these being the first games from this decade I'm interested in)