To begin with, revan was a master with both the light and dark side of the force, and was also one of the strongest force users (he beat Darth Malak while malak was drawing on an immense amount of darkside energy from the star forge)
And, the Jedi Exile's charisma, as stated by Kreia, mostly comes from the ability to easily make force bonds. And don't forget that the Jedi Exile was immensely powerful too, being able to beat three Sith Lords, two of them by herself.
SO revan had a kind of charisma the exile didn't have, and, also, revan beat vitiate, no easy feat.