Bioware's first magnum opus, and the title that helped establish them as the true kings of Western RPG design, along with delivering new, fresh gameplay mechanics that would elevate this original instalment over Obsidian's (still great) sequel.
One of the best fits for the Star Wars mythos is RPG gaming in general, and letting you create your own character from scratch before throwing you into the deep end of the universe is still one of the best ways to experience Lucas' rich fiction, regardless of any medium.
As Gamespot reviewer Greg Kasavin noted at the time; KOTOR was (and we'd say still is) "one of the best things to happen to Star Wars in many years. It's arguably a better property than the two most recent theatrical films it's just a fantastic role-playing game all around." Naturally, you can throw Revenge of the Sith into his comment too.
Even after receiving a spin-off MMO that worked to varying degrees, it's this original single player-focussed adventure that's one of the most absorbing and rewarding in the entire genre.
Which has been your favourite over the years? Let us know in the comments!