The debate is hot and heavy: who is the best quarterback in New York’s N.F.L. history?

All anybody can say for sure is that Eli Manning, with two Super Bowl rings for the Giants, has accomplished more than any other New York quarterback. But is he better than Joe Namath, the Super Bowl III icon whose Jets justified the American Football League? Better than two of the Giants’ previous championship quarterbacks in the modern T-formation era, Phil Simms and Charlie Conerly? Better than Y. A. Tittle, a two-time N.F.L. most valuable player with the Giants?

After watching professional quarterbacks as man and boy for more than six decades, I’ve always hesitated to rank them, say, 1 to 10, for several reasons.

As essential as a quality quarterback is, he doesn’t “win” a Super Bowl; he’s merely on a team that wins a Super Bowl. His success depends on how well his linemen block, how well his receivers get open and how well they catch his passes. It depends on how well his defensive and special teams units do their job. Quarterbacks are not golfers or sprinters or skiers. They’re not out there alone.

As much as anything else, a quarterback’s success also depends on how well his skills fit his coaches’ offensive system.