Muhammad Ali is the greatest of all times because he fought wars in a more competitive era...he fought the best, and he beat the best. His record would have been far more impressive if it weren't for him being suspended 3 years for not participating in the Vietnam War. It's just too bad he didn't know when to retire. In his prime, Trevor Berbick or Larry Holmes wouldn't have had a chance. Tyson doesn't belong on this list. Losses to Holyfield 2x and Lennox Lewis were all horrible...he couldn't beat anyone relevant. A matter of fact, replace Tyson with Evander Holyfield. I'm not a fan of his, but he is a warrior...4x champion. Last, somehow, you have to put Manny Pacquiao in that top 10 because the man has 8 division world titles. You cannot ignore that.