While I feel BG2 is the best cRPG ever, I have to agree with Steel_Wind here that the Revan twist is exceptionally good. It really is one of my best gaming moments, I was actually chuckling during the confrontation, thinking "Oh my! Oh my! Woho! Oh my!".
It was a like-a-child-on-christmas-eve experience.
Also, let's not forget the fact that it's Star Wars, people. That alone gives it an edge - The Jedi have a "coolness factor" of 11 out of 10. Swinging a lightsaber, to me, is cooler than a sword any day.
I have to admit I place KotOR relatively high on my list, there's just something about Star Wars when it's done right (too often it's not). KotOR (maybe 2 as well) is probably the only Star Wars game I feel have a good enough story and background to truly exist in the SW universe. More often than not there's some silly element that makes me go: "Eh? George Lucas would never write that, it doesn't fit at all!".
KotOR suffers a bit from the Aurora 2,5D issue though, much like The Witcher. Not having a true Z-axis means you have to run around fences and have cut off zones, instead of actual jumping and free movement everywhere. Invisible walls is a big issue.
My dream RPG is probably Gothic gone KotOR, or KotOR gone Gothic (depending on perspective). A rock solid Star Wars RPG with Gothic atmosphere and exploration. I've been dreaming about such an RPG for years.
I'd say KotOR is probably the 6th game on my top ten RPG list, with BG1-2, Gothic 1-2 and PS:T above it. All these games have exceptional replay value, fun combat and a well written story. If KotOR had been built like Gothic 2: NotR, it would probably be my all-time favourite, or at least be in the race with BG2 for the top title.