White Knight Chronicles.
I don't know why I was so interested in this game to begin with. Maybe it was simply the fact that it was a new JRPG (developed by Level 5, no less) exclusive to the PS3, a system which I didn't own at the time. I thought, "If I had a PS3, I'd get that game for sure."
So I got it.
Every aspect of the game is so poorly implemented it really astounds me. It's not specifically terrible at any one thing, but it's bad enough at everything (story, characters, voice acting, combat) that there was no way I could compel myself to finish it.
Well, either that or Legend of Zelda: Phantom Hourglass.
Five words: TEMPLE OF THE OCEAN KING. The surefire quickest way to make me lose interest in a game is to make it time based. And I know the whole game isn't like that, but the whole damn game just feels like backtracking to that stupid temple and playing through it ad nauseum.
Oblivion deserves special mention in that I really don't like it, but it's less the fault of the game sucking and more just me not getting into it. I've tried replaying the beginning four times and each time I've never gotten far. I wish I liked it, but I just don't.