Pavlik/Abraham Kessler/Taylor Cotto/Margo II I'm sorry but although those are awesome match-ups, let's be realistic, neither of those would be huge among the general public enough to even come close to record-breaking numbers.
the biggest fights that can be made are the ones which involve boxers well-known by hardcore, normal and casual fans alike. they should also have massive fan support in their own countries and have fought numerous times in the US in large PPV events. there are currently only 3 boxers (excluding dlh) who fit this criteria : mayweather, pac and hatton. any fight involving these three will easily rake in more than 1M PPV buys.
from a financial point of view: Hayes vs. Wlad Pacquiao vs. Mayweather Pacquiao vs. Hatton as to a fight of significance and a probable financial standpoint as well: Margarito, Williams, or Cotto vs. Mayweather for welter supremacy Pacquiao vs. Marquez III to settle this madness once and for all Wlad vs. Valuev for undisputed heavyweight championship of earth