I dont consider Ali to be the greatest of all fighters p4p all time either. He is a great boxer no doubt about it but there where people in the lower weight classes who did just as much if not more then Ali.
Oh and by the way a prime Tyson was very very difficult to beat for ANYONE he had a very good defence and you not only had to work that out...you have to avoid being ko'd as he had soooo much power and speed.