Really wish I could have seen Johnny Unitas week in and week out in his prime. I would guess very few folks on this forum are old enough to make that claim. Not to mention, you would have needed to live in the Baltimore area to get his games on TV. Directv was something nobody could have even imagined back then.
I say this because it's hard to say "Joe was the greatest, period." We haven't seen ALL of the greats, and you cannot go strictly by numbers based on how the game has evolved. But I think Johnny U (and most other great QBs) could be great in any era. Great quarterbacks and great running backs of the past, IMO, would be great today. It gets a little more dicey with other positions. Could Jack Lambert play MLB in today's game at his playing weight of 215? (Put aside advanced nutrition and weight training and supplements ... I mean just take Jack Lambert circa 1975 and plop him into a modern day defense). I think he would get swallowed up by the enormous guards of today. Could great DBs from the 50s and 60s cover some of the great wideouts today? I'm not so sure.
Sorry for rambling. Just typing out loud. I guess the bottom line is, if you gave me the choice of ANY quarterback in history to win one game for me to save my life, the other ten players on offense being equal, I'd choose Joe in a heartbeat. Understand, he's not the best thrower I've ever seen. That would be Dan Marino. It took your breath away to see Marino throw a football. Lighting-fast release with a vapor trail attached to it. And Elway was no slouch either. But Montana was the best winner I've ever seen. I have so much respect for his game.