I have to agree that it would be Revan. Revan was a proven tactician who fought a real war against a real bad ass opponent (the Mandalorians). He basically destroyed the Mandalorians and they NEVER recovered from Revan's victory.
Darth Vader's rage and anger was becase he feared losing his wife while Revan's rage and anger was the result of fighting a losing war and willing to sacrifice himself in order to win and protect the galaxy. Vader was selfish to the core unlike Revan.
Oh and on top of that Vader had to live in his suit because he was practically chopped to pieces while Revan only wore his outfit to make him more menacing. Revan fought was a proven general who fought years in war like a good soldier. Anakin was a wimp compared to Revan.
Yeah but that doesn't really deal with the plot of the games, or so I heard. It would be great if there's gonna be a KOTOR 3...and I suppose it would be great too if I didn't go off-topic. So...yeah. Revan all the way.
Oh and one more thing about Revan that I completely forgot.
Revan's views were the reason why there became a "Rule of Two". Darth Bane was given credit for the "rule" but he only got the idea because Darth Revan is the one who said it in his holocron. (Read: Darth Bane: Path of Destruction.) It's Revan's legacy that Anakin followed as Darth Vader... the long-time apprentice of Darth Sidious. Anakin NEVER rose to the level of Master (either as a Jedi or a Sith).