Probably the lower half of the top 10. I think he tends to get overrated due to the comeback. What he did at his age was amazing, but I'm more impressed with fighters who stay active and fight tough opposition, and may be done at an earlier age.
My Top 10: 1. Louis 2. Ali 3. Holmes 4. Lewis 5. Frazier 6. Liston 7. Tyson 8. Marciano 9. Johnson 10. Foreman