The Sakuraba v Ryū thing is mostly because Sakuraba has the one thing Ryū has yet to reclaim: ball mastery (dribbling, immaculate first touch etc). Being able to walk past players like they're not there is obviously a tremendous skill to have, but if that's all you've got, you'll eventually hit a wall.
Kobayakawa is definitely a good rival for Ryū right now, and is a much closer parallel to Ryū too. A good example is how both of them have trained their dead ball abilities to visibly high degrees.