Here is your answer. For the second straight year, Michigan-Ohio State was the highest rated regular season college football game. (And for people who think that college football's lack of a playoff is an unmitigated disaster, find me a regular season game from the MLB or NBA that comes close to a 6.4.)
Reading Sports Media Watch this year has been fairly illuminating for me. The biases of ESPN make more sense when one reviews the ratings and sees that, yes, Michigan and Ohio State do draw higher ratings than other teams. Similarly, the Yankees and Red Sox draw banner ratings when they play one another. ESPN drives me absolutely crazy when they focus all of their attention of the Yanks and Sox, but in the rational part of my brain, I have to tell myself that they are simply giving their customers what they want.