Headed into last season, the Pac-10 was the conference of running backs. It still has some good ones -- Jacquizz Rodgers and LaMichael James jump out -- but right now, the true running back conference is the one that once gave us Tony Dorsett, Ray Rice and Curtis Martin: the Big East.
Football Outsiders uses one metric called POE (points over expected); more than yards or yards per carry, POE and Adjusted POE (adjusted for offensive line play) combine a runner's ability to break long runs, score touchdowns, and produce at a level higher than what an average back could achieve given his carries and set of opponents.
You can find more on POE and Adjusted POE by going here.
This output-versus-expected-output approach is a reliable method for adding context -- opponent quality, offensive line play and more -- to a running back's production.