I do not think Justinian deserves the title "great". I would say that the reconquests were more despite of than because of Justinian. His distrust of Belisarius almost lead to the loss of Italy after it had been reconquered. What do you think?
It would have been interesting if Justinian had a daughter. If so, would he have been wise enough to make Belisarius his son-in-law and heir? That way he could have made sure that his descendants would have been close to the throne, while the empire would have got an emperor that truly would have deserved to be called great, Belisarius the great.