The few Cubans in the pro ranks were all products of defection. The vast majority of successful Cuban boxers throughout history never had the chance. Amateurs don't always translate to Professional success, but with the massive amount of talented amateur boxers at Cuba's disposal throughout the country's history, one can only imagine that there must have been an Ali, a Tyson, a Lewis, a Sugar Ray, a Oscar De La Hoya among them.
They clearly would have made a mark. A nice couple of world champs, maybe a ATG here and there. But certainly wouldn't always have succeeded like you see happening now, with some of their olympic medalists failing to make their mark in the pro ranks. Certainly in the higher divisions they would have trouble, in wich power and chin trumps technique for the most part.