Those fights that would be the most widely watched worldwide, provide the biggest PPV numbers (more than 1 million), fill an arena and make the most money for the promoters, TV networks and the fighters themselves. NOT which is the fight that the small niche of purists would like to match or watch. For instance Calzaghe vs Jones does bigger numbers than Calzaghe vs Dawson.
DLH-Hatton by a mile 2nd group: DLH-Mosley III DLH-Tito II DLH-PacMan Hatton-PacMan Hatton-Mosley Mayweather-Mosley Mayweather-PacMan Mayweather-DLH II Some of these are unlikely but these would do stunning numbers.
De La Hoya/Hatton De La Hoya/Mayweather II De La Hoya/Pacquiao De La Hoya/Trinidad II Hatton/Mayweather II Pacquiao/Mayweather
Jones vs Calzaghe Hoya vs Tito II Pac vs Floyd / Hatton Hatton / Hoya vs Floyd Hatton vs Hoya Klitschko vs Klitschko
I would call the biggest fights available those that would do over a million in PPV and fill an arena. Many of those listed so far could not do that.
Current Calzaghe vs Jones Pacquiao vs Mayweather MMA Fedor Emelianenko vs Randy Couture Anderson Silva vs Cung Le Runner up-(comes close) De La Hoya vs Hatton Hatton vs Pacquiao In 2009 Mayweather vs Cotto Calzaghe vs Pavlik If Anderson Silva ever fought Roy Jones that fight would also be in the "Mega" category.