Win the "Clubber Lang vs. Rocky Balboa 2" match in Historical Fights mode to unlock Joe Czak.
Win the "Rocky Balboa vs. Cluber Lang 1" match in Historical Fights mode to unlock Dave Fossan.
Win the "Rocky Balboa vs. Mason Dixon" match in Historical Fights mode to unlock Mason "The Line" Dixon.
Win the "Mason Dixon vs. Rocky Balboa" match in Historical Fights mode to unlock Rocky V.
you must beat all the matches and story mode (the match with apollo vs ivan drago)
Win the "Apollo Creed vs. Ivan Dragon" match in Historical Fights mode to unlock Apollo Creed from Rocky IV.