joe did a fantastic job. Unfortunately he didnt have the same quality of opposition a the likes of Hagler, Leonard, Duran , Hearns. THere are different era's in boxing and Some greats fall into Joe's catrergory, likes of Joe Louis. Louis beat everyone there was but there wasnt really anyone of class oppostion that he beat. Most were lightheavyweights such as Conn or Ezarrd Charles, or Joe Walocott who was an old man. Louis himself was old when he got KO by Marciano.
If Joe Calzaghe beat Chad Dawson (best lightheavyweight) then yes we could call him an all time great in the same league as Hagler, Ali, Marciano, or Salvador Shanchez