Re: Games started but never beaten.
Borderlands 2 (but only because of a glitch
Assassins Creed 3 (piece of shit)
final Fantasy X
Metroid Prime 3 (takes 5 hours to get to final boss, I died. never tried again).
Pokemon Diamond/Pearl (worst entry in the series)
Oblivion (I did all other quests except the main quest)
Perfect Dark (I finished it eventually (like 10 years later))