Guys like David Shaw, Chris Peterson and Gary Patterson come to mind. Even Dantonio, who had a bad year last season, is in that tier. Franklin?
BUT
Would those guys leave their spot for a job at Tennessee, LSU or Nebraska? That is the big question.
Dabo is probably in that first tier. Maybe Fisher?
Saban is not in a tier. Saban doesn't need a tier. He's in his own world, with Bryant, Paterno and the other all-time greats.
1st tier is Urban, Fisher and Dabo.
2nd tier is much bigger and includes guys I mentioned above, along with guys like Richt, Snyder, Gundy, Mullen, Leach, Gus, Petrino, Ferentz, and yes, Jim Harbaugh.
Not sure what to do with guys like Fitzgerald and Cutcliffe, and then the other guys who have not done it very long but show great signs.
Then you have a guy like Bielema. Good coach, good program manager? Was his success in Madison because of the program his boss built? It's starting to look that way from where I sit. Where he sits might be getting a little hot.
This reasoning is why I'm not including the current UW coach in that tier - yet. We'll see what happens, but I do know he's had to remake/correct a lot of things when he got back home and that he's not done yet.