Sonic the Hedgehog 2006. Up until that point, 3D Sonic had been pretty good. Sonic Adventure, Sonic Adventure 2 Battle, and (To a lesser extent) Sonic Heroes were all enjoyable. Then Sonic 06 came out as quite possibly the most incomplete game ever released at full retail, and the name of 3D Sonic has been cursed ever since. Luckily, Sonic Unleashed came out two years later and was great, (Yes, it's great. IGN be damned) but it's still hard to get over how terrible it truly was. What's even more terrifying is the fact that I got all the achievements for it. I'm still not sure why.
Honorable mentions:
Star Wars: TFU 2 (A step back from the first game in every concievable way)
Halo 3 (Bland, repetitive campaign and unbalanced multiplayer)
Perfect Dark Zero (The game just plain sucks)
Honorable mentions:
Star Wars: TFU 2 (A step back from the first game in every concievable way)
Halo 3 (Bland, repetitive campaign and unbalanced multiplayer)
Perfect Dark Zero (The game just plain sucks)