I'm afraid I'm gonna have to agree that Richter would be the weakest of them. He got fucked up bad by Shaft, and true, Simon got cursed but at least he broke it himself. Richter on the other hand had to be saved, by Alucard. I just don't think there's anything ''special'' about him. And it doesn't matter he saved a lot of ladies, because in the end each and every Belmont saved the whole damn world and every human being living in it.
Personally I'm gonna vote for Simon, for the same reasons everyone else has. He fought Dracula twice and he broke his own curse. Not to mention he looks totally badass in his Chronicles remake design. I don't really see why so many people disaproves of it. His design fit in much better in the Castlevania world compared to the old-dumbnut-rock-eating-wife-beating-crapping-in-a-hole-in-a-cave-brute-warrior. And even if the new Simon look kinda femenine he at least doesn't look like a homosapiens.
EDIT
Oh sorry, I was going for "neanderthal" there XDD