Madden's winning percentage is in the top 5 in NFL history. You know what his record is against other coaches in the Hall of Fame? According to Wikipedia, a remarkable 36-6-2. Of course, considering the source, I don't know if that's accurate.
I'm old enough to remember him at the tail end of his coaching career. Remember that Madden retired because a) He didn't like to fly, and b) he had a bleeding stomach ulcer his last year in Oakland. He retired before his 43rd birthday. Somebody tell that to Bill Parcells.