I can see your point but with the Dempsey/Willard fight since i was about 11 I always wanted to see in person the smaller man beat a much bigger man a super-heavyweight if you will. If though I was to pick a fight that had no surviving footage of it may well be greb - Tunney (I)
Ali-Frazier I Leonard-Hearns I Leonard-Duran I HM's Walker-Flowers Schmeling vs Louis I B. Leonard-Mitchell II Leonard-Benitez Foreman-Lyle Marciano-Walcott Pretty unoriginal list, but these would be the ones I'd want to see most.
Lets say that an angel appeared before you, and actually made this offer. It would be a absolutely horrendous decision on your part, if you wasted the opportunity on a fight that was filmed. History would damn you for that!
Johnson-Jeffries. Just to see the look on the faces. Leonard-White. Dempsey-Firpo with class. Greb-Gibbons III - Front row. 4 rounds in the middle of a f-ing storm. Greb-Norfolk I - The carnage. Zivic-Armstrong II - The homicide's heart in all it's depth. And more carnage. Walcott-Choynski - A dwarf kicking the sh*t out of a LHW. Can't even imagine. Also any Jack Blackburn's, Young Griffo's, Holman Williams's, prime Dixon's,...
I understand this point of view, but at the same time, watching a fight on Youtube, and actually being at the fight in person are two completely different experiences. To me, it's reasonable that someone would actually want to be at Madison Square Garden on March 8, 1971 to see undefeated champions Ali and Frazier square off, even if it meant having to sacrifice the opportunity to see Greb or Burley.
You know what, if it's just 3 they'd be much more obvious: SRR-Bell, Leonard-Welsh II & Greb-Tunney I.