I think we would have to scratch our heads over that one for a long time Kendall! As a boxing technician, powerhouse and relentless stalker of his opponents, there is a lot to support your nomination of the young Mike Tyson. By the time he fought Buster Douglas, not all those tools were still in place. He reminded me of Frazier in many ways. They were both very compact fighters and neither of them was particularly big (for a heavyweight).
It is hard to identify a really memorable heavyweight at the moment. The Klitschkos are adequate world champions, but to my eyes their boxing skills fall well short of those we have seen in the past. At the lower weights there are still some tremendous world champions.
I wonder what criteria you would come up with for "greatness" as a heavyweight? You have probably seen a few more than I have!