Yes Alexander would have been as great in peace as he was in war because he founded the Olympic Games for maintain peace and uniting in Greek cities.
Alexander the Great (one of the greatest ruler in the history) was the Greek administrator. He is also known as Alexander III and Alexander Macedonian. From his ruling time to till the death he had won about half of all the land which the ancient Greeks knew.
During his time, he had conquered the territories of Iran, Syria, Egypt, Mesopotamia, Finland, Judea, Gaza, Bactria and Punjab in India