Oh my, where to start?
Final Fantasy VIII.
After VII rocked my socks, I'll admit my expectations for VIII were probably never going to be met. However, the game just too damn long to get anything done. Every little "walk to the other side of town" moment was plaqued with dialogue and moments of utter stupidity.
Going off mission, risking the lives of your friends, and leaving the fate of the world blowing in the wind... to apologise to someone for being mean? Yeah. Ruined.
Call of Duty - Any title after Modern Warfare.
Call of Duty was a revelation; cinematic action heavy gameplay, that still knew how to give you those heart-in-throat moments. COD2 wasn't as good, COD3 was a piece of shit, but COD4 knocked it out of the park. And every game since then has gotten worse, dumber and less fun. Remember when Call of Duty used to attempt to be semi-realistic?
Resident Evil 5.
Depsite any claims to the contrary, Resident Evil 4 still remains the best in the series. 1 and 2 were terrific - and still are - but nostalgia blinds, and tank controls with a fixed perspective aren't much fun any more. Resident Evil 5 decided to become Gears of War, without anything that made Gears of War actually fun. I had no fun, at any moment, playing this game, and it remains a candidate for the worst game of this generation.
Real Time inventory? Co-op focus... in a survival horror game? The second worst companion A.I. in a hyped game (Hi, Daikatana!) of all time? A confusing menu system that treats you as inferior if you're playing single player?
Crysis 2.
If Crysis 2 had of been called anything other than a Crysis game, I'd slap a big 4 star banner on that baby and recommend it to my friends. However, it did stick a Crysis sticker on the box, and unfortunately this is possible the worst shooter sequel since Farcry 2. Gone is... everything from Crysis. In its place is a console centric menu system, console centric multiplayer, console centric graphics engine, and a story that is actually worse if you've played the original game. Flying ice testicle monsters? Gone. Alien grunts that look and act like very Military Shooter bad-guy since Modern Warfare? Check. How did they fuck this up? Seriously.
Supreme Commander 2.
The worst RTS sequel of all time. That includes Command & Conquer 4. Let that sink in for a moment. The single player campaign was somehow even worse than the shit the first game gave us! But the worst thing that ever happened was to the gameplay. Gone was the scale of the first game - because fuck people who like your games, right? Everything that was good about the first game was removed, in favour a poor selling Xbox 360 version that left the developer in such a bad state financially they had to sell off one of their own I.P.s to keep the company afloat. Consoles have destroyed a lot of series - this is one of the few I'll never forget. I play the original. It's literally better in every single aspect. No exceptions. None.
Deus Ex: Invisible War.
It's as bad as you've read. It destroyed Deus Ex, and nearly left the series completely abandoned. Luckily, Human Revolution came along and revived the series by basically ignoring this title. Every thing it does is an item to ensure you never do with a sequel.
Grand Theft Auto IV.
We were promised a gritty, dirty tale - a new direction for the series, that focused on realism and consequence. What we got was 15 hours of fetch quests, side missions that were even more mindless than the single player campaign, and a broken multiplayer system. At least the city was cool. For about an hour.
Starcraft II.
Industry leading production values. The worst story, characters, plot and dialogue I've seen in a game that takes itself seriously since Ultima IX. The Terran-focused balance system means if you're not playing Terran, you're doing it wrong. The lack of a meaningful single player campaign means the game is utterly worthless. Blizzard finally made a bad game. And burnt whatever good will they had left.
Diablo III.
Real Money Auction House. What else do you need to know? Prepare for the great shit storm of our time.