Most coaches will admit that Paul Brown is the greatest coach ever, and the father of the modern game.
George Halas must be on there. Shula passed him for the win record, but if you look at Halas's stats, there was one season where he only coached in 5 games, and 7 or so where he coached in only 11. Halas still had 318 regular season wins.
Shula is 3rd. 2 superbowl wins, 6 appearances, most wins, 1 perfect season.
The fourth spot.... I understand the argument against Belicheck, but still, what he accomplished was unbelievable. If I am excluding him, I have to go with Lombardi. Look at how many NFL championships he won before the Super Bowl ever existed, and he even won two of them.
Landry, Noll, Walsh are banging on the door.