Muhammad Ali had it. Magic Johnson had it. Michael Jordan had it. LeBron James has it. Steph Curry has it. Tiger Woods had it, back in his prime anyway.
Awareness. Understanding the moment, understanding the game, the ability to sense things long before they ever happen. For Ali - it was his ability to sense where the next punch was coming from and countering based on his opponent's tendencies. For Magic - it was his innate ability to see the entire basketball court and sensing exactly where his teammates were on a fast-break. For LeBron, Curry and even Tiger - their respective abilities to block out everything going on around them long enough to focus on a specific target.
And in Peyton's case - an awareness of his teammates, his ability to sense the opposing defensive schemes, his effectiveness with utilizing great judgement in changing certain plays on the fly from the line of scrimmage, and knowing what to expect the moment the ball was snapped.
You don't get mentioned in the same sentence with Tom Brady, as often as Manning does, and not be considered a great player. For most of his career, Peyton controlled just about every game he played in. Even in the Super Bowl a few months ago - he at least had enough awareness and showed enough control to not make huge mistakes and let the Patriots steal the win. Considering the player that he's been all these years - it had to be tough swallowing his pride in that last game and recognizing that he needed to play his diminished role in the shadows of a great defense that would hold them steady.
The argument that he should've won more Super Bowls is valid, indeed, but he's got 2 of them. I take nothing away from Peyton simply because he happened to be on a team with the best defense in the league last season, no more than I take anything away from Russel Wilson the year Seattle won with not only a heralded defense, but also six pro-bowlers on the roster that season.
It was a great ride, Peyton. Enjoy your retirement - you've more than earned it.