The Pride of Wales in a very close contest although Fury may overtake him should he beat Usyk to become undisputed.
Lennox. Calzaghe a close second although his fear of flying seemed to disappear whenever a fighter was past their prime. His opponents over a 9 year stretch between Eubank and Lacy were pretty much all crap.
Lewis for me. Undisputed HW champ that cleared a talented deep division at the time. A record that consists of wins over Hollyfield, Tyson, Vitalli, Mercer, Tua, Golota, Tucker, Morrison, Bruno, Briggs, Rahman and Grant. Had two losses which he avenged (granted the Mccall avenge was under very controversial circumstances as Mccall shouldn't have been allowed to fight).
Jack 'Kid' Berg should be on the list but I'd agree with @Noel857 on the top five although I would place Lennox at 5th with Fitz and Ted Lewis at 3rd and 4th.
For pure boxing brilliance and overcoming career threatening adversity it has to be Joe for me, it's just a brilliant story, the last of the old school.
I'd have thought Calzaghe, and by a country mile. Lennox number 2. Froch must be high up the list, Hatton also. John conteh top 5 perhaps?