i'd say simon as well. if i recall this correctly, julius did state he had a lot of help. simon went it alone, never leveled up once(like you know julius would if they made his game), and destroyed dracula single handedly. then upon being cursed, single handedly traveled the country side finding dracula's pieces, to put him back together, and destroy him again.
julius somehow obtained the knowledge to seal dracula, but that doesn't mean any other belmont before couldn't have if they came upon the same knowledge, which doesn't automatically put him at the top. for all the praise soma gives julius for doing the impossible, you don't know that he wouldn't have seen, say trevor as a god or something. not to take away from julius, i'm just saying we don't know if an older belmont couldn't have done what he has.
chrsitopher gets a nod though, just for the hell he's gotta go through just to reach dracula, while moving the most sluggishly a belmont ever has.