I think everyone will agree when I say that Joe vs. Max could have potentially changed the world. So in those terms aside from Jeffries vs. Jackson I can't see any other fight doing so.

As for the history of the sport any one fight can change the history drastically when you think about it. But for the sheer impact I think Tyson vs. Douglas is the biggest.

Sanchez vs. Gomez
Arguello vs. Olivares
JCC vs. Martinez
Lopez vs. Rosendo 1
SRR vs. Maxim