Nagano Olympics for N64
FarCry: Vengeance for wii
Return to Castle Wolfenstein on PS2 (not the pc or xbox versions, which I hear were much better)
Goldeneye: Rogue Agent
Those are the only games I can think of that have seriously disappointed me. Keep in mind I was 10 or 11 when I got Nagano. I've played some other gloriously
awful games like the 3D remake of Paperboy for N64, but games like that have a special place in my heart.
I got Farcry: Vengence thinking "Come on, it can't be that bad. After two or three games, they've gotta have the FarCry formula down by now, right?" WRONG. In their defense, I'm sure they were more focussed on Crysis at the time, but still.