Muhammad Ali might have been the greatest heavyweight of them all, but that doesn't necessarily mean he would have beaten every other heavyweight champion.
It's true that styles make fights, as Ken Norton -- who is not considered a great heavyweight -- showed in his three tough, close fights with Ali.
Size comes into play, as well. Some of the modern heavyweights would have been much bigger than Ali.
Ali's greatest assets, of course, were speed, reflexes and mental and ...