One of your earliest sentences said it all - the SEC and the B10 are so very similar. These 2 conferences epitomize college football for me (an OSU fan). I could watch a Saturday of nothing but SEC and B10 ball and be more than content. The other conferences have interesting games, but in the B10 and the SEC, each game is an EVENT.
The Midwest and the South are where the heartland of America is, both regions grew up with similar values and culture, and college football was an outgrowth of those. B10 and SEC fans are far and away more passionate, have larger fan bases, and live and die more with their team than any other fans. I don't view these 2 conferences as rivals, I view them together as the foundation of college football.