Pretend for a second that you're a sports writer/fan in Chicago/New York/Philly/Boston/Baltimore and you're asked to list the biggest rivalry games in college football -- being from those areas you begin with Notre Dame - USC and then to Notre Dame and whoever they're playing, then where do you go?
You go to Ohio State and Michigan - you go there because unlike Purdue - Indiana, Texas - Texas A&M, Alabama - Auburn, USC - UCLA, Cal - Stanford, it matters. You go there because unlike Texas - Texas A&M, or Alabama - Auburn, it's an amazingly even series, because BOTH schools have impressive histories - not just once every four years - because so much rests on the outcome.
Name another rivalry where so many awards, bids, championships ride on the outcome -- that's why you count down to Michigan week, that's why you laugh when they stumble bum to Appy State, just as the folks in Ann Arbor were hoping Navy or Marshall could pull the upset in the 'shoe.