The Xenosaga trilogy. Yes, I do have all three of them, and I never made it more than an hour into any of the three. Most of the characters just completely do not resonate with me. And I know there's merit in being slow-burning, but holy balls can we pick it up a little bit or have something interesting happen, please? I own these because I love Xenogears and figured they were a no brainer. It's made me reluctant to pick up Xenoblade, honestly.
MGS4. I'm a big fan of 1 and 2 (couldn't stand 3, I know right). I've tried 4 about...5 times and I just can't do it. I hate what happened to the controls, mechanics, and flow of the game. Oh, and that "gameplay" is hardly what it's shooting for in the first place. And the cutscenes seem to be directed by a Quentin Tarentino locked in a room for a month with a sheet of acid and an encyclopedia of military history.