PFF (subscription required) is a website that grades out players both in the nfl and college, they are the pinnacle of this and nfl teams use them in player contracts and this is what the league, media and players uses to judge. Recently they increased their reach to college (insane that they judge every player's snaps) They ranked the top returning BIG players, Ohio State and Michigan State tied with 3 players.
MOD EDIT - Providing site link here:
https://www.profootballfocus.com/blog/2015/08/08/ranking-top-10-returnin...