How are you judging their greatness? Length of reign, how fast they won the title, quality of opposition (which is kind of a vague one as styles make fights), number of wins, number of defenses?

My list has always been 1. Joe Louis (longest reign & most title defenses) 2. Rocky Marciano (perfect record) 3. Muhammad Ali (some of the biggest wins in division history)...after that it's a mixup of Holmes, Foreman, Lewis, Tyson, Wladimir, Dempsey, Johnson, Holyfield, Patterson, etc