SUPER BOWL XLIV Final Score: Saints 31 Colts 17.
Even with this loss Manning, in my opinion, is still the best QB to ever play in the NFL.
Both Manning and Favre have a lot of similarities, staring with one Lombardi and a tendency to throw picks at crucial moments.
How many times has Manning thrown a pick at a crucial moment? If his pick Sunday was the only time, then how can you call this a tendency? Do a little research and you'll find that Manning has thrown interceptions on a lower percentage of his pass attempts in the playoffs than Joe Montana.
Manning threw a lot of picks for Tennessee at crucial situations.
Name three of those situations. Again, one situation by itself does not prove a tendency.
Who has the better postseason W-L record: Manning (9-9) or Montana (16-7)? I rest my case. 
And here I come to shoot down your case. Football is a team sport, a TEAM SPORT, I tell you. No one player is solely responsible for whether his team wins or loses. Therefore, the QB very often gets too much of the credit when his team wins and too much of the blame when his team loses. IOW, a QB's W-L record is vastly overrated as a statistical measure of a QB's effectiveness.
Teams QB'ed by Montana defeated teams QB'ed by these QBs: Ken Anderson, Boomer Esiason, Jim Kelly and John Elway. Manning ... Rex Grossman.
There. Fixed that for you.
In addition, you're overlooking those playoff games where the only reason Manning's team didn't beat the other QB's team in the Super Bowl is because they played in the same conference--for instance, Tom Brady. (Interesting that Brady QB'ed the losing team in playoff games against both Mannings...)
For the top 10 NFL Postseason QBs, visit here. Elway is on the list.
You're merely citing someone else's opinion, though. I prefer to go somewhere like
www.pro-football-reference.com and conduct my own statistical analysis.
FWIW, I mean nothing in the above few posts to disparage the legacy of Joe Montana, whom I credit as the best QB, and one of the three best players at any position, ever to play in the NFL. I just cited his record as a baseline for comparison on one or two key stats. I never intended to make any case that Manning is somehow equal to or better than Montana in any way. Peyton Manning is truly one of the greatest QB's to play the game, but Joe Montana simply set the bar for "greatest ever" so high that Manning still has a lot to do to reach it. I thought that before the Super Bowl two days ago, so his untimely interception does nothing to change my opinion.