The rules nowadays are so skewed in favor of the offense it's comparing apples to oranges, when comparing Peyton Manning to Fran Tarkenton.
Best physical qualities in a QB I ever saw was John Elway, the guy has a rocket and the mobility to escape serious pressure. He was captain comeback, performed when it counted most, he could've won those superbowls with a less stunning RB than Davis, TD was great, but that OL was cutting fools to pieces, the RBs who preceded him just weren't even in his ballpark, let alone league in Denver imho. FYI I hated the Broncos, and Elway for many years, I'm over it now and can appreciate him a little bit more.
Montana had the most accurate pass ever either on the run or in the pocket, he was a great leader, but had an owner with a massive payroll and great supporting cast, I don't hold it against him, he still had to lead them to the promised land and he did it exceptionally well.
Marino was a great leader, cursing out his players when not putting for the effort or screwing up a pattern was awesome to watch. His release was quicker than Warners, better than Jeff Georges imho. He has way above avg arm strength, and RIDICULOUS toughness.
Those 3 mentioned above all had great qualities, leadership and toughness being off the chart qualities I hold in high regards.
IMO,
1. Montana
2. Elway
3. Distant 3rd Marino
4. Fran
5. Favre
I second the Kenny Anderson Cincy QB as "most underrated", he was dang good for a few years, on a junk team, and came up just short against imho, the best QB ever on a far superior team.