Several years ago at the HOF induction. Marvin Hagler told him that he respected him. Even though Hagler was showing him respect, McCallum tried to take Hagler to task and asked him why he didn't fight him. Needless to say Hagler was completely surprised and caught off guard by Mike's question. Pretty classless on Mike's part considering McCallum wasn't in the picture at middleweight until after Hagler retired and NOBODY was clamoring for a Hagler-McCallum fight at that time. Mike was pissed off because he never got the massive payday that the Fab 4 got. He would have had more credibility taking Tommy Hearns to task who was active at 154 when Mike was.
How can someone dare to question. The man took the LMW Division by Storm, Forget about Julian Jackson, Milton McRory, Terry Norris who became known as he won against SRL, Don Curry, stepped up and made 6 defenses of the WBA MW title against guys like Steve Collins, Michael Watson, Sumbu Kalambay and others b4 facing James Toney for the IBF title which I believe he won, the official result was a draw, and the rematch result which was also controversial, later on he would school Jeff Harding who battled so hard with Dennies Andries in 3 fights and the only loss up then to RJJ and another in his trilogy to James Toney at CW. One of the All Time Greats and a Special Favourite of Mine, The Body Snatcher or The Professor.
Unequivocally great. You can't even put together a credible argument for him not being great. He is frequently cited as exemplary of why some opponents were great (Toney & Jones for beating him; Kalumbay, Watson and Graham for being competitive) and he decisively beat some guys that are widely acknowledged for being very good if not great: Curry, Harding, Collins, McCrory, Jackson, Kalule. He is a consensus h2h pillar (as in very few in history would be comfortably picked over him) of two weight divisions. Ridiculous even questioning his greatness.