I don't think it's possible to determine who the "best" of any athlete would be. They are all different, played differently, did different things, etc. It's like asking who the most beautiful woman in the world is.
Emmitt has had an unbelievable career, thanks primarily to his good health, great talent, and outstanding support of his teammates. He deserves to have the rushing title, because he DID it.
Barry, Emmitt, OJ, JB, Sweetness, Dickerson, Riggins, Leroy Kelly, Marcus Allen, Priest Holmes, Csonka, Gayle Sayers, etc., etc., etc.-I'm glad I got a chance to see them all play. And, no doubt, I'm leaving some out.
Emmitt-thanks for everything. You are One Class Act...