Namath, Stabler, Sloan, Barker were all great field generals who could really energize their team when the game was on the line. All did very well as a starter in the w-l department.
For the combination of talent and leadership, though, I'd give Namath the edge, then Stabler, Barker, Sloan. Namath easily had the best arm, his biggest flaw was that he sometimes felt there was no coverage his arm could not beat.
I am proud to have seen all these guys play, and they all represented us magnificently.