This list isn't in order.

Sugar Ray Robinson
Floyd Mayweather Jr
Harry Greb
Jimmy Wilde
Henry Armstrong
Willie Pep
Muhammad Ali
Sam Langford
Joe Gans
Archie Moore
Julio Cesar Chavez
Jack Johnson
Roberto Duran
Joe Louis
Benny Leonard
Gene Tunney
Sandy Saddler
Micky Walker
Sugar Ray Leonard
Thomas Hearns

Theres 20 boxers who will always be rated higher than Calzaghe i think people are going over the top. And are forgetting about other great fighters from the past. In fact i could name another 20 boxers who all have a case to be rated higher than Calzaghe.