The difference between him and the next best RB during his era was probably the biggest difference between a top guy and the next guy of any position in any sport of any era.
I'd take Babe Ruth in that particular discussion, with Gretzky a close second. If you're talking individual sports, too, I think Tiger and Federer have been more dominant, as well.
I'm not sure I'm enough of a sports historian to know, but who was the next bes RB during Brown's era?
Ruth and Brown have something in common, which is that it took decades and juiced up athletes to brea their records. (Well Hank Aaron and Maris probably weren't, but you see what I mean)
But during his day Lou Gehrig was not too far behind him. Was Jimmie Fox around? Didn't he hit like 58 homers once?
During Gretzky's time there were other good players. Bobby Orr was just a little before Wayne I think Tiger had Phil. Hard to argue with Federer.