Joe Calzaghe v Roy Jones Jr.
1999-2001. A fairly new WBO champion against a legend of his era at his peak. Through my Welsh rose tinted specs, I'd give Joe a good shot at it, because of workrate, punches thrown, and his granite jaw. RJJ would probably have the class to edge it, but I would see it as a pendulum type fight, with momentum swinging back and forth, and maybe, just maybe, Calzaghe getting a SD.