Well that's only your view but the game has it as Dante finally surpassing Vergil(since he was sought to be the "older" brother and the more stronger of the two.) I'm just going by what it shown at the end of DMC3 and DMC1. Also yes Dante did have to win but we are talking about if Vergil was actually as strong as him in the first place at the end of DMC3-DMC1 were it ended. See now if someone put it as Nero vs DMC3 Dante then we can theory and speculate about it because it has never happen and will never happen, but in Vergil case it already has happened.