The difference being that Revan actually was given a character - that character can basically boil down to this.
Kotor 1: Revan was a Sith Lord. He died, officially. He was a great strategist but betrayed us all.
Kotor 2: OMIGOSH REVAN IS SO AWESOME HE THE GREATEST JEDI EVAR.
Seriously, if Canon Sue ever applied anywhere, it applies to Revan. The only worse ones I can think of are Eragon and Edward Cullen.