In the sixth century, Justinian accomplished the brief recovery of the empire’s old territory in the east, in Africa, and in the west. His victories, however, were hard won over the course of decades, and they came at a great cost in human life, not to mention taxation. Paradoxically, Justinian’s military successes probably contributed to the empire’s subsequent decline. The conquered lands were hardly secure, and many were lost in the years after his death. During his reign there was a great flowering of Byzantine culture, whose monuments remain in Istanbul (e.g., Hagia Sophia) and Ravenna. His reconstitution of Roman law, the so-called Justinian Code, is still the basis of civil law in some modern states. Justinian is venerated as a saint in the Orthodox Church.
Justinian was okay, but his wife - Theodora - had, ahem, religious problems: she conspired to make the infamous Liberius pope so he could teach Monophysitism. He didn't.
(Theodora was, by all accounts, a petite woman. A very bad sign.)
I'd rather be the Holy Roman Emperor Frederick I Barbarossa. Far cooler guy.