SEC vs. Big 10 Rivalry Goes Only One Way
(Los Angeles, California)
Your statement "that biggest rivalry between college football conferences has been between the Big Ten and the SEC" indicates that you are an SEC fan.
As a second-generation Ohio State fan now living in Los Angeles, I can tell you that Big Ten followers universally regard the PAC 10 as our rival conference.
Just because the SEC has been the self-proclaimed "best conference" in recent decades does not create a rivalry. Recall that for 50 years (from 1947 until 1997) the winner of the Big Ten went off to the Rose Bowl to play the PAC 10 champion. Chants of "Rose Bowl! Rose Bowl!" were common battle cries in Columbus, Ohio and other Big Ten stadiums after emotional victories.
For many decades, conference losers did not play in any bowl game--it was the Rose Bowl or none at all. In later years, Big Ten losers would go off to get trounced by the winners of other conferences, but that did not create a rivalry.
Although most Big Ten followers are well aware of the great football traditions at Alabama, Georgia, Florida State, Miami, Tennessee (etc.), the great majority cannot tell you which conference they are in.
Is Miami in the SEC or the ACC? What about Florida State, Georgia and Clemson? Big Ten and PAC 10 fans do not know. No college football fan in Michigan and Ohio ever needs to look up which conference the USC Trojans are in.
Every Big Ten fan that I know considers the PAC 10 to be their rival conference, and visa-versa. Do most SEC fans consider the Big Ten to be their rival, or is that only your opinion?
The arguments you make for why they should be rival conferences (North vs. South) are logical; however, the feelings that actually create such a rivalry are not prevalent among Big Ten fans.