This is my personal choice based on the persons career and my boxing knowledge.

1. Joe Lewis
2. Muhammad Ali
3. Larry Holmes
4. Lennox Lewis
5. Evander Holyfield
6. George Foreman
7. Joe Frazier
8. Mike Tyson
9. Floyd Patterson
10. Riddick Bowe

This list was complied using boxrec, but boxrec has some sugar-list, so this is
the real deal. What does the forum think, I think it's quite spot on.