Peyton Manning may have the stats but he does not deserve to be in the equation for a top-5.
His record in Indianapolis was inflated by playing two atrocious, expansion-level teams twice a year (I'm talking about the Texans and the Titans). This was an almost guaranteed four wins per year.
Manning's playoff record is actually really terrible. Most years, his teams were one and done. 9 times. His overall completion record, interception percentage, etc, are worse in the playoffs than the regular season. He played worse in big games. Almost every year.
Look at his stat logs from the one season he won a Super Bowl with the Colts. In the playoffs he threw 3TD passes and 7 picks. Yes, 7 picks. In one of those games he went 15-30 with zero tds and 2 picks. Defense bailed him out.
Same scenario the year he won a title with the Broncos. His stats were terrible but the defense carried the team.
Brees is or will pass him up in stats, and if Brees wins another title, I would put him above Manning for sure. Brady is the clear #1, not sure why anyone would argue that. Maybe Montana #2. After that, it gets harder for more "modern" era quarterbacks.
For the old schools guys, it's clearly Bart Starr. In a league that didn't favor passing, he set records that still stand today. He still holds the highest postseason passer rating. Dude was a winner.