You're a fan and know it.
Was Jim Brown the best running back of all time. or was it Payton.... or was it Smith....
I vote for Smith, cause I'm a Cowboy fan. I think if I played pro ball I'd of been afraid of Brown. But if you ask the SF safety Lott who he hated to tackle more than anybody.... Walter Payton...why you ask? Cause he did this nasty little thing called "finishing the run"...just before he gets tackled he'd square up, bow up and plow into you.... ouch.
Running backs are about yards, but really quarterbacks are about championships. Like I said, it's not fair, but it is what it is.
Marino will have the stats till Manning (you pick) will break all of his records as will Brady. Then he'll be the second best or third best of all time.
The only way to accurately compare QBs would be to figure out how to evaluate them in the same systems and with the same personnel around them as every other QB. This is not possible, but I've long felt that Marino would have played well on just about any team -- and with just about any decent offensive line around him. He was not mobile at all, so he would not have been effective the way someone like Joe Montana was, but he would have been a Hall of Fame quarterback under almost any scenario I can envision.
As far as running backs go, I'd have to go with Walter Payton -- and by a wide margin, too. Not only did he retire as the NFL's all-time leading rusher, but he did so while playing most of his career on pretty poor teams. And he was one of the NFL's all-time leading pass-receivers, was an exceptional blocker in the backfield, and even threw option passes well enough that he served as the Bears' emergency quarterback if needed (he had about a half-dozen TD passes in his career).