Probably Final Fantasy XII, but that's a very personal opinion.
Youre a bad boy, arent you?
No hard feelings. (I love that game.)
A couple real purchases come to mind. (I also have a small handful of games from my reviewing days for a small PC game site, and those sometimes sucked, but they dont count as games I intentionally own.)
1, LOST (PS3). In my defense it cost me $2. However, I still gambled thinking I might somehow enjoy it. Rest assured, even as a huge LOST fan and someone who even admits the game has pretty nice graphics, that I find this game to be horrendous on every essential level.
Side note, it has Sawyer voiced by some random guy, sounding like the rapists from Deliverance. (It DOES have some real LOST actors in key roles.)
2, Frank Herberts Dune (PC). This was an impulse buy before I knew about Internet reviews and, like, the first time I had money I earned transfer this could freely spend on a video game. It looked interesting, and I love the source material, not to mention that classic Dune 2 (the innovative RTS from Westwood).
This game is absolutely inane on every level. Jesus. Im not even a guy who likes to criticize stuff. But I mean wow, what the hell?! I dont even know how to describe the genre, its so utterly generic.
Over the past couple of generations Ive generally geek careful about buying fairly highly rated games, so honestly ending up with actual bad games is not that likely. Disappointing, sure. Mediocre, sometimes. Overrated, yes. But not actually bad.
With one more exception.
3, Assassins Creed 3 (X360). Motherfucker, this game was actually bad. Story, not good as a finale. Main story missions, both awfully linear and shockingly buggy somehow. Main character, not a pleasant fellow to find oneself controlling. Side content, totally run of the mill.
Worst of all, it squandered the American revolution by presenting it amateurishly. Thats a horrible sin (which they reportedly repeated with Unity, which was supposed to cover the French Revolution, probably the most interesting piece of history EVER).
Yeah, normally reviewers are more or less okay in my book... but AC3 is not an 80s game. Come on.