The one thing would be all purpose yards. He's #8 all time with almost 20,000, and pretty much everyone else in the top 10 is a HOFer. Of course Brian Mitchell is the exception, and he's the all time return leader, so it's hard to imagine Sproles getting in and not Mitchell.
I think most people would agree that Sproles was much more of a real offensive player and overall threat/talent than Mitchell, who was truly a specialist, but Sproles numbers aren't miles better. I think Hulky is right. Not a Hall of Famer.
So bdog is wrong. Not one of the all time greats.