Revan. No contest, in my mind. Revan started wars, destabilised a galaxy, hovered in the grey area between Jedi and Sith, proved both doctrines wrong, set out to save a galaxy by making it destroy its own corrupt government and was just plain freaking badass. Also, Revan was trained by Kreia, who was fucking immense, and even made an enemy of the Exile - or rather, that's how I interpreted the story behind the series.
Galen is angsty. Galen is boring. Galen has overly-dramatic set pieces controlled via Quicktime Events. Galen can rip a Star Destroyer from orbit because the devs wanted to script someone strong. Revan is as strong as the player. Revan manages to have a kickass personality despite having no lines of dialogue. Galen has no personality and terrible dialogue. Revan didn't need a love interest. Galen has a horrible one.
Yeah, Revan wins.