Dragon Age I. I beat something about half of it, got extremely bored with it, and I left it to be unfinished. Then my friends actually beat it, and they kept telling me it was awesome, so I picked it up again, finished it... And I still didn't like it. At all.
1) The story was bland, generic and every single plot point was just predictable.
Alistair: I have to tell you something.
Me: Oh God, please don't tell me you are the rightful king of this place, or something like that.
A: I'm a King's bastard.
M: Crap...
And many other examples including the final twist.
2) Characters (with exception of Zevran and maybe Morrigan) were so terrible, I would let them all go, if I didn't need a tank/mage/whatever in my team. I'm still baffled that so many people like Alistair (Swooping is bad? Really? You're laughing at that stuff?), Leliana lacked any interesting charcter trait, I cannot even remember anything about Oghren at the moment, Sten's saving grace was his Polish voice actor, who's talent helped me bear with him, Dog's potential as a companion was wasted, and in my books, Wynne kicked out G0-T0 from KotOR 2 from "worst companion in a western RPG game" throne.
3) Gameplay was meh at best. People praised challenging combat, but my mage turned out to learn the most broken spells in game (Cone of Cold was seriously OP. I don't know if it was a glitch or something, but I'm pretty sure at one point I managed to hold Archdemon in place with it), so I breezed through it. The like/dislike system basically forced you into certain squadmates composition depending on personality you used in dialogs (this thing was solved later in DA II, so at least they learned a bit), and anything else just didn't really stand out in any way, positively or negatively.
I remember the favorite part of the game for me was the Sloth Demon dream prison. I thought that was FINALLY something fresh and interesting, changing forms to open up new areas made me feel a little bit like in a Castlevania game, and the companions dreams were a nice way to actually give them at least some life. Then I heard that one of the most popular DA mods let's you skip it. Yeah, either I'm just from the bizzaro world, or this game just wasn't meant for me.