alot of these guys are better fighter than rocky, but few are better boxers. like duke said in the new one "you know everything there is to know about fighting". its not about tactics or anything because rocky knows it all. hes the best brawler around, and apollo taught him speed and agility enough to take on even mr t.
drago is likley above peak human strength because he uses steroids, so hes stronger than any human can naturally be. and rocky doesnt just take his punches for a while, he takes them for 12 rounds. nobody on the list can take as much and keep comming. and he even wins in the end.
the guys on the list train to fight, they use elbows and knees and feet, rocky is just boxing, he has more experience in just using his fists than anyone on the list, they wouldnt really be in their element in a boxing match. i can see rocky getting to the end standing, he might lose on points to the likes of batman, but i dont think any of these guys could put him down for the count.