Talent-wise its plain and simple. It's OSU then Michigan then everyone else in the BIG. The distance between OSU and UM is pretty wide too (@QB, RB and the secondary)
WISC in the west is the most capable team to put up a real fight against the Buckeyes. They can eat up clock, score and have the OL and DL to compete 4Q with them. However, I still think they would be 10 point dogs on a neutral field.
I think Nebraska can/will compete eventually BUT its going to take a few more cycles of players. Need a talented experienced OL and DL (meaning a few 1st & 2nd all BIG players) a STUD QB who doesn't turn it over and a speedy D that creates turnovers. I think getting RBs and WRs in this offense is very doable. QB, OL and DL recruiting is going to make or break it.
Right now nebraska is pretty far off from that. A young OL, the DL is adequate but lacking a pass rusher (might be lucky to have a 2nd team ALL BIG player here), and a good QB who is turnover prone. On top of that add in a spotty defense and problems in the kicking game.