My entire premise is that football coaches are, far and away, more important than in any other sport, at least the major US team sports, and if he's the best there, he has to be the best out of all of them. And your entire premise is ridiculous. I'm not diminishing his abilities, but, just to point out one flaw in this argument, he coaches FAR fewer games every year than coaches in every other sport. Again, just argue for him being the best NFL coach ever and be happy with that. Nah, he's right on. The lack of games per season just makes his job that much harder. All of these coaches have a full week to prepare against one another. They cannot rely on one talented player winning the game singlehandedly, nor can they excuse a loss by saying you just can't stop that guy. Every game is life or death. Baseball coaching is a psychological affair, and basketball coaching is just hoping for ping pong balls. Hockey coaching is just yelling at guys to be tougher and then making sure you handle line changes properly. Football is a max effort sport but also one where strategy matters, and they have a real salary cap. To be able to dominate it for so long is a testament to at least a generational standout of a coach, and probably an all-timer.