The big slugging heavyweights leave me cold but the tactical, intelligent heavyweights, and the lower weights who have trained themselves mentally and physically, and treat a contest as a test of skills are the kind I love to watch.
Even better when the contestants know it will be an evenly matched contest, and will likely go to points; it's not just a case of looking for the lucky big punch.
Sugar Ray Leonard is probably my all time favourite, but Julio Cesar Chavez was another, and of course the legendary heavyweights Hagler, etc
And Nigel Benn was always great to watch because you never knew when his heart was going take over from his head and the tactics would go out of the window :-) But I never missed Barry McGuigan, Naeem Hamed, even John Conteh! Too many to list. I would watch with my Dad..my earliest boxing memory is Henry Cooper!
I couldn't find anywhere to watch Bruno v Tyson in 1989 and had to listen to it on the radio - it was just as memorable an occasion even listening!
For me it's about athletes and tactics and skill - no one wants to permanently damage their opponent, though of course it happens.