Bastila has a very compelling character. On the surface she seems haughty and shallow (which in and of itself is unusual for a Jedi), but she obviously has some inner demons regarding the Force and the Jedi Code, and her game-long battle with it makes for a very interesting character.
You don't see that kind of thing in the films. In the films it's all either 'lol light Jedi' or 'lol dark Jedi' or 'lol light Jedi that becomes dark Jedi.' The lol's are for emphasis. >_>