I'll go Kalule, Kalambay, Collins for the other 3. Could argue Harding and Yonker cause they were at LHW.
1. Sumbu Kalambay Best fighter he beat. It was a close fight, it could have gone either way, and Kalambay had declined from his late-'80s peak. It was nonetheless a terrific technical performance, and I'd take middleweight Kalambay over the junior-middle versions of Curry or Jackson. With this win, McCallum moved to 40-1 and avenged the 1 on his record. 2. Julian Jackson Underrated win at the time, as no one knew who Jackson was, and the fight had no hype behind it. Turned out that Jackson would go on to a HOF career, and this was his best weight. It was Jackson's first step up in class, but it's not like he didn't yet have the power that made him a world-level fighter. Jackson was 29-0 heading into the fight, and at one point McCallum would represent the 1 in a 46-1 fighter who had accumulated titles at two weights. 3. Donald Curry Curry had been a dark horse candidate for best fighter in the world just a couple of years before this, and he did win a world title at 154. He was not on a run of strong performances heading into this one, but he looked quite good before McCallum flattened him. I don't know whether Curry's looking good for four rounds makes this a better or worse win. One of two HOFers defeated by McCallum. 4. Jeff Harding Did you know that Harding was the only reigning champion McCallum ever defeated? This was his last fight, and he'd been inactive for a while going into it, but McCallum wasn't a natural LHW and he got a UD over a man who'd been a solid champion at the weight. 5. Herol Graham I'd take middleweight Graham over Collins or Watson. I think that the scoring in this fight was a bit generous to Graham, especially the one judge who gave McCallum only two rounds. I think that the first three wins are all about equal, and then there are about five separate wins that could go in the last two spots. Watson, Collins, McCrory, and Kalule were at the same level as the guys I put at numbers four and five. Kalule at junior middle was a really good fighter, but he had declined quite a bit when McCallum fought him.
McCrory, Harding, Watson McCrory was game but overwhelmed. Curry had starched him but he was still a very good fighter. Harding was naturally 175 and very strong, McCallum was in no way a natural Light Heavyweight but the difference in skill was immense Watson was a very good middleweight and had knocked out Benn in the battle of Brittans but McCallum knew a little too much for him and broke him down
Aside from Jackson and Curry, I think his other wins below are some of his best. Mike was a top caliber fighter. Sumbu Kalambay Michael Watson Herold Graham Jeff Harding Steve Collins
Sure, he beat Jackson and that was big but let's also remember the victory over Jackson's trunks is about equal.
Julian Jackson = Taking big punches in the 1st round against one of the hardest punchers of all time, then coming back to stop him in the very next round very impressive performance. Michael Watson = Beat Nigel Benn & came within a whisker of beating Chris Eubank twice. McCallum showed he was a level above Watson as he systemically took him apart in a wonderful performance. Donald Curry = McCallum's best knockout of his career a picture perfect left hook. Sumbu Kalambay = Revenging a loss to one of the most underrated Middleweight champions of the last 50 years. Jeff Harding = McCallum winning a tough but clear decision over the tough aussie Light Heavyweight champion with McCallum winning a world title in his 3rd weightclass.
