Interesting. Possibly just outside of the top ten for me, or scraping in. I rate him 6-7 at the moment.
For me, Foreman would always be an all time great, but of course, I mainly became a huge fan of his when I was growing up watching his comeback, so it does have a great deal of value to me. I think his wins over Frazier, Norton, and Lyle, along with his all time win/ko ratio would make him among the best. He also won the gold medal and lost only two times in his first 47 pro fights. Foreman is probably my favorite heavyweight of all time, or at least one of them to be sure.
As it is I'm not sure Foreman should be top10, he had too much missing from his game, same with Frazier, both fighters showed very apparent weaknesses
I probably wouldn't have him in my top ten if not for the comeback. A true ATG shouldn't fizzle out while still in his prime like he did after Zaire. By that time he had only met six good fighters and lost against two of them. But by coming back in such fashion he showed true heart and amazing strength of character. What complicate matters is that even though he had some amazing physical assets and some amazing mental assets, he never had them at the same time. It's only by combining young Foreman's physical gifts with old Foreman's character and heart that you get a truly great fighter.
He would be a bit of an enigma. Some people would have ranked him in the top 10 based on what he did to Frazier while others would see just too many unanswered questions to rank him in their top 20.
I presently have Foreman in my top five at heavyweight, but the comeback is a big part of that. It's what separates him from other "intimidating destroyer" champs with devastating-but-brief title runs. With no comeback, Foreman would probably rank near the tail end of my top 10.