I think if we give Sam the WR that Warner had, the offensive line that Warner had, and Marshall Faulk and Mike Martz as coordinator that he would be pretty damn good.
It's not fair to Sam to make the comparison given that Sam's #1 WR, Gibson, would have been a #5 on the GSOT.
I love Steven Jackson, but he didn't have the home run potential that Faulk had everytime he had the ball in his hands. SJax could gain yards when Faulk couldn't, by moving the pile, but Faulk added a dimension that very few RB in the history of the NFL was able to do.
Roger Saffold would never be able to do what Pace did.
And during the GSOT era they played a system that accentuated Warner's talents.
Put Sam on the 1999 Rams and see what would end up happening.