who is considered the best heavyweight boxer of all time?
['MUHAMMAD ALI. 56-5 (37), 1960-1981. ... ', 'JOE LOUIS. 66-3 (52), 1934-1951. ... ', 'JACK JOHNSON. 56-11-8 (36) , 1897-1931. ... ', 'ROCKY MARCIANO. 49-0 (43), 1947-1955. ... ', 'GEORGE FOREMAN. 76-5 (68), 1969-1977/1987-1997. ... ', 'JOE FRAZIER. 32-4-1 (27), 1965-1981. ... ', 'JACK DEMPSEY. 54-6-9 (44), 1914-1927. ... ', 'LENNOX LEWIS. 41-2-1 (32), 1989-2003.']