I don't buy the Southern football is better than Northern football, but I do buy that the Southern schools have devoted more resources to winning than the Northern schools. And I do buy that Southern high school players are more fully developed in high school than Northern high school kids. (And it certainly helps the SEC schools by over signing and running off players.)
Think about this. Have Northern schools like Syracuse, Pitt, Rutgers, Maryland, Purdue, Indiana, Minnesota, ... ever hired (and paid) top football coaches? Penn St had an elderly Joe Paterno way past his prime. (Clearly, PSU is on the upswing with the James Franklin hire.) Michigan has floundered over the past few years with bad coaching fits. Honestly, the only Northern school that has been totally committed to football over the past decade has been Ohio St. (West Virginia and Cincinnati have had success with good coaches, but the coaches eventually left.)
Compare this to the SEC. South Carolina, never a power in the SEC, hires Steve Spurrier to become relevant. LSU hires Les Miles after floundering for a few years. Alabama hires Nick Saban to rebuild the program. Texas A&M hires Kevin Sumlin. Arkansas hires Brett Bielema from Wisconsin. And on and on.