Robot Wars for GBC a long time ago, obviously you don't expect much from a gameboy game but this one absolutely dire and barely playable.
Worst PC game I bought was a game called Castle Strike, it looked great but turned out to be a crap version of age of empires.
FIFA 05, scored a goal from the half-way line, took it back
Need for Speed Carbon - PS2 at the time -- absolutely terrible..
Diddy kong racing nintendo ds
Crappy try to make another Mario Kart
I found Burnout 3 pretty dissapointing.. i know it got near perfect scores from all the critics, but it just wasn't entertaining at all for me. All the tracks/modes felt so empty and pointless. Like there was no progression for the player involved. Oh and some of the worst choice of music i've ever heard in my life. Makes you yearn for the days of catchy 16-bit game music, or even 8 bit!
rome total war - gods how boring, im a general i kill things not a bloody accountant