Obviously, Peyton is one of the greatest QBs in NFL history. Top 5 all-time for sure, and hey, maybe he's #2.
But a threat to overtake Joe Montana at the top of the mountain? C'mon let's get serious. Montana's record speaks for itself, (two time NFL MVP, 8 Pro Bowls, 273 career TD passes, over 40,000 career passing yards, all time passer rating of 92.3, etc; etc.)
But what separates Joe from other QBs, and all but a handful of other professional athletes in general (although Michael Jordan and Bill Russell come to mind) is his almost supernatural ability to reach peak performance when the pressure is on, the game is on the line, defeat or victory hang in the balance.
I know pretty much everybody here is aware of this stuff, but just contemplate for a moment Montana's spectacular achievements: Super Bowl record: 4 wins, 0 losses. Three time Super Bowl MVP. All time playoff record 16-7, with 45 post-season TD passes. 31 come-from-behind victories. And so on.
Sorry, no disrespect to Peyton Manning or Tom Brady, Johnny Unitas, etc, but but there is not another QB in NFL history who can match that kind of magic. The guy not only just refused to lose, he always had a path to victory and could show his teammates the way there.
IMO, any Joe Montana 49er championship team beats any Peyton Manning Colts team 9 times out of 10.