I still vote for Jim Brown. Unmatched combination of speed, power, skill and attitude.
Just reading his background on the SU website, Three Hall of Fames, Unmatched at his position, and probably the most durable running back of all time (never missed a play in 9 years in the league).
He was a decathlete, finished 5th in the 1954 national championship with a couple of guys named Bob Mathias and Rafer Johnson ahead of him.
I believe he still holds the all-time HS basketball scoring average record for Long Island, nearly 60 years later.
This link says it all
http://www.orangehoops.org/jbrown.htm