That guy is either praying or attempting to kiss is a$$ good bye at high speeds.

I'm going to have to say Barry Sanders just because I never had the privilege to watch Jim Brown.  I also would throw Emmitt Smith's name into the discussion because he absolutely ran all over my Eagles.

I have been waiting for someone to bring up Emmitt Smith.  He benifited from a 15 year career, with 16 game seasons.  He averaged 4.2 YPC, one whole yard less than Jim Brown and .8 yards less than Barry Sanders.  He only missed 14 games, 7 of which were in his last 2 seasons with the Cards.  He caught 2.3 passes per game.  Dalas had one hell of a line when he was younger so he racked up a lot of yards then.  He did have longevity so you have to respect that.  Heck, impossible to really say which is the best of these since they were each unique in their own way.  I saw all 4 play, but only watch Brown in his last 2 years when I was young.  He was punishing and just hurt people when he ran.  You nead to realize he weighed around 230 when all pro defensive ends weighed 240 and DT were 250-260.  LB were 220-230.  Do not think one could go wrong with any of these 4. 

One not mentioned was Gayle Sayers.  He also averaged 5.0 YPC but only played for 5 full seasons with one cut short.  Fast, smooth, he could give a tackler a limp leg and be gone.  Knees destroyed and he was gone.

Damn, you really know your stats! Payton may not have had the numbers of Brown and Sanders, but he made up for it with consistency and versatility (at least in my book).

Nah, not Payton 4.4 YPC.  A toss up between Jim Brown 5.2 YPC and Barry Sanders 5.0 YPC.  Jim Brown had a higher YPC than Sanders but he was from an earlier era before athletes got larger and faster.  Sanders lowest YPC year was his last year with a 4.3 YPC average.  He was always on a marginal Lions team stacked against the run with a below average passing game.  Jim Browns lowest year was also 4.3 YPC but he played 4 years when there were 12 games and 5 yars with 14 games per year.  Then again, it depends on what one means by "greatest".  If you include receiving yards in the mix, Jim brown only averaged 2.2 yards per catch but this was in a time where backs did not catch many balls.  Barry Sanders caught 2.3 balls per game but again, a poor passing team.  Payton averaged 2.6 per game but he caught many screen passes.  JMO with facts to support my position.  hehehe