Froch is greater because he has fought the better opponents and also has the better wins, add that he is not even done and can still add yet another win over Bute and can beat Kessler by decision if it's in Nottingham; he trumps Calzaghe's resume. If they were to fight like in 2007-2008, i'd favor Calzaghe.
Pascal, Taylor, Bute, Johnson, Abraham, Reid.
Hopkins, Kessler, Bika, Reid, Lacy, Eubank, Jones. Calzaghe didn't really fight any one dangerous worth mentioning.