I like a few, but Max Schmeling is my favorite to watch. He had such an entertaining style, because he combined smart pressure with excellent counter punching, something which is not often seen at HW. Schmeling could box, he could swarm and he could even brawl. He had very interesting defense to study and his right hand was extremely powerful for his size. I also like the way he broke down opponents without unnecessary agression, he was always calm inside the ring. He's not the greatest and he's not big enough to fight at HW today, but who cares? I still believe that the masterclass he put up against Louis is the greatest performance in HW history (just over Joe Frazier FOTC).
Bob Fitzsimmons is my favorite but I can only get a little footage of him on Youtube. Otherwise it is Holyfield who is my favorite to watch.
Larry Holmes, but Foreman and Ali are not far behind. This might sound weird, but if Foreman had stayed in the game in the 70s, fought Holmes and beat him, he'd be my favorite heavyweight. But since Jimmy Young beat (and knocked down) George, I'm confident prime Holmes would have stopped him imo. Larry was the Champ back when I was super into boxing, and I was obsessed with his jab and the way he dismantled so many of his opponents. I loved watching guys like Ocasio, Weaver, Jones, Weaver, Neon Leon, and LeDoux actually look pretty good against him early on, then get drunk and mugged (hard for me to get the image of the prime, wickedly twisting, nasty Holmes jab out of my mind). To me only Ali and Louis were greater.
Foreman, Lewis, Louis, Ali, Frazier, Marciano, and in the last few years Charles has really grown on me. Fury will make the list, but its not right to mention him in that pantheon just yet.
Kid Blackie sure was a great and if he had defended the title more often then yes he would be my favourite, but 6 defences in a 7 year reign tarnishes the legacy for me. However from a boxing history perspective him and his era are probably the subject/time which i have read most about.