I've posted this before, and so have other people, I believe. But since joining the Big Ten (1993), here are all of the teams' conference winning records (not including 2013):
0.778 Ohio State 124-35-1
0.750 Nebraska 12-4
0.681 Michigan 109-51
0.638 Penn State 102-58
0.609 Wisconsin 96-61-3
0.509 Iowa 81-78-1
0.503 Michigan State 80-79-1
0.459 Purdue 72-85-3
0.438 Northwester 70-90
0.322 Illinois 51-108-1
0.313 Minnesota 50-110
0.225 Indiana 36-124
So Penn State is leading the charge of the 2nd tier teams, at 4.5 games ahead of Wisconsin. Although, it might be argued that Ohio State is alone in the top tier, with Michigan leading the 2nd tier teams, as they are 15.5 games behind Ohio State, and Penn State is only 7.0 games behind Michigan.
(The purpose of this was to point out that Penn State is NOT in the middle of mediocrity, as I believe someone else posted. But they're also not on the same level as Ohio State, as was maybe implied. I'd be interested to see how Penn State compares to the rest of the conference since about 2000 or so.)
(Edit: For the record, in my opinion, it's crazy to think that Penn State is Ohio State's rival. The MAY become a rival (not on Michigan's level, of course), but it will take a lot of time and a lot of competitive games to reach that level, though.)