This here is a question which I know everyone will disagree with me on. But if we're really considering the "best quarterback" and factoring in the other 10 players (remember this ain't lebron's NBA) who are key to a team, I think its best to go by the era. (As much as I respected Terry Bradshaw and 4 superbowls, no way in hell) I think the shortlist is:

80s: Marino/Montana
90s: Young
00-10s: Manning/Brady

- DeflatedPucks[don't ask me to go back further, I hate joe namath's guts)

My pick is: Marino (personal fave: steve young)

In a similar way if you had asked me the best running back, Emmit Smith would not be it. (btw, i would say Sanders)

Bart Starr of the 60's. The 70's had Fran Tarkenton, Ken Stabler, Roger Staubach to name a few better than Bradshaw.

I have met Joe Namath and he is a very cordial guy (I golf with one of his brothers). Having said that, my mother went to BFHS and one of my aunts graduated with him and apparently he was a jerk in high school. Also listening to some of the stories that his brother tells us, it would be tough not to be a jerk with the way people put 'Joe Willy' on a pedestal.