Mine would have to be Knights of the Old Republic (yeah, I'm late, I know.) Story had that great twist, but other than that was kinda standard. The dialogue suffered from the usual problems...
Choice A- give away all your money, your ship, and your equipment to fund an orphanage.
Choice B- do absolutely nothing, and get no alignment bonus.
Choice C- commit galactic infant genocide while abusing cute animals and profiting off enslaved factory workers...all at the same time.
I played the evil route because I heard it had a great ending-and it does. The problem is most of the evil dialogue options just seem...stupid. It made my character seem like a more extreme version of a cartoon super villain, being evil for little reason at all, whereas everything but the dialogue painted my character as someone drawn to the dark side for the power and wealth, not just because he likes torturing puppies.
Gameplay was good, the lightsaber fights were pretty great, and with the difficulty turned up it could pose a challenge at times. Unfortunately the final fights were incredibly easy for me, whereas some sand people on Tattoine managed to beat me senseless every five seconds earlier in the game. Kinda messed up that the ending boss gets ground under my boot with hardly a struggle, but some primitive tribesman managed to slaughter me.
I'd give it an 8/10. Flawed but good.