There's these guys:
Bo Jackson
James Brooks
Carnell Williams
Ronnie Brown
Stephen Davis
Tucker Frederickson
Joe Cribbs
Rudi Johnson
And now Tre Mason. Where is he in the list of top running backs of all time?
Hard to say, different offenses, different eras. In terms of pure physical skills (strength, size, speed, etc.) I would put him behind several on that list. In terms of non measurables (vision, heart, nose for the endzone) he's nearly as good as any RB we've had.
And I would add Ben Tate to your list of great Auburn running backs. Not his fault he got stuck in the Tony Franklin experience his junior year, in his one year as "the guy" with a competent offense around him he had 1300+ yards.