Muhammad Ali 1974-77 Muhammad Ali 1963-66 Rocky Marciano 1953-56 Mike Tyson 1986-89 Joe Frazier 1969-72 Joe Louis 1938-41 Joe Louis 1944-47 George Foreman 1970-73 Larry Holmes 1978-81 Sonny Liston 1960-63 Floyd Patterson 1958-61
How you rate their records during that particular period, taking into account the quality of the fighters they defeated, or lost to (if any). The style of their performances and the manner of their victories…KOs, comfortable points wins etc.
For the particular periods listed I'll go with the following Ali 1974-1977 - Quality wins Tyson 1986-1989 - Level of devastation against the top guys of the era. Louis 1938-1941 - Quantity of wins with his own brand of devastation. It was a tough call for third with young Ali, Frazier and Liston also doing very good work