^idk about "a lot" of people...even if its a weak era the heavyweights are no joke, unlike any other division virtually everyone has a potential punchers chance or size advantage in some capacity (reach, height, frame, weight, etc). In todays day and age when everyone is colossal, defense, stamina, and technique are king. It would require a guy who has not only a good chin and power, but has a firm grasp on the basics and ring generalship. Unless you're godzilla you arent going to dominate the heavyweight division for years on end with raw power and size alone. Jim Jeffries, Willard, Carnera, and Max baer tried it, Foreman tried it, Ruddock, Tua, and Valuev tried it, its impossible.
I actually think Ali could have surpassed Joe s record if he hadn't been stripped. He'd already made I believe 9 defence s and up to frazier coming along I can't see anyone in that time frame defeating Ali. And of course with out the exile he may well have defeted frazier.
25 defences of a belt will almost certainly happen. 25 defences if a legitimate title claim will almost certainly not.
It's certainly not unreachable. But considering boxing's present landscape in which boxers don't fight particularly often, I don't see it happening anytime soon. However, that could change in the future, of course.
If we're talking about defending "one lineal belt" and NOTcompiling title fight wins through a myriad of different belts and divisions like say Julio Chavez did ( who incidentally has over 30 ) then I'd say it's going to be tough. As Mendoza pointed out, you'd likely have to have a younger champion of exceptional talent and long term focus coupled with some soft touches. Even Joe Louis had the advantage of being able to preserve his title status during wartime along with facing a few second raters here and there.
Yes should have to be quite young when winning the title, then be similar to a Louis or Holmes with a division most up of older fighters and second tiers. And still have the skills and abilities to see off the younger generation coming through. But to get to, 25 defence s or more?? That a tough challenge. Proved how good holmes and Louis were!!