Duke Nukem Forever and Aliens: Colonial Marines.

I hope one day Gearbox Software will pay for their sins in the hell. Especially that guy Randy Pitchfork for his lies and false advertisement. I can't understand how gaming studios cant be punished for false advertisement. There should be justice for these things.

Pretty much re-iterating what most others have already mentioned.....

Master of Orion 3
Armed Assault 3 (technically vastly superior to AA2, but with so little content, and nothing but droves of overpriced DLCs being introduced - in another 10 years when AA4 is out, and AA3 is done with DLCs, there will be an AA3 GOTY edition containing the lot for a reasonable price - AA3 will finally be the game it should have been from the start!)
Deus Ex Invisible War (ok by itself, but when contrasted to the original Deus Ex..... whooeee)
Blood 2 (one of the worst games ever written)
Campaign 2 (managed to be worse that the first - this probably IS the worst game ever written)
Flight Sim X (left unfinished by MS, code usurped by greedy developer, became a DLC money pit)
Supreme Commander 2
Heretic 2
Empire Earth 2
Empire Earth 3 (x10 times worse than 2!)
Doom 3
Quake 4 (one of the stupidest FPS games I have yet witnessed)
Descent 3 (the new system just didn't work for me)
KKND 2 (dross, the very incarnation of dross!)
Unreal 2 (a disgrace to it's father)
FarCry 2 (constantly respawning enemies, and always in the same in the places? Boooooring and tiresome!)
Stalker : Clear Sky (nice idea but just did not work within the Stalker game engine)

Commandos 2 was pretty disappointing. It was too easy and had too many unnecessary gimmicks that looked nice but didn't really enhance gameplay.

Summoner 2. Playing Summoner at a friend's house made me buy the PS2 after avoiding it for so long, and it was awesome in spite of its flaws. Summoner 2 was wrong in so many ways, not the least of which was completely different combat (standard real-time hack&slash vs. turn-based with minor real-time components) and the fact that the main character wasn't even a summoner (she was a shapeshifter). I ended up forcing myself to finish it, and it wasn't that terrible a game, but it sure was a disappointment. Not as much of a disappointment as Fallout 3, but that one's already been covered.