It's tough to argue Bo v Herschel. Bo had more foot speed but Herschel was a beast and could run nearly step for step w/ Bo. With that being said it would be tough to argue that Cam Newton wasn't the "best" player of all time either ?
For me it was either Cam Newton or Michael Vick.
I went with Vick, but it was a close call. As I see it, even Cam Newton couldn't have done what Vick did against FSU in the BCSCG game -- which is single-fricking-handedly keep a highly highly overmatched team in the game.