re: In your opinion, who was the greatest leader in history?

Augustus Caesar gets my vote, and he should have more votes in this thread.

Augustus Caesar was the first and greatest of Rome's emperors, having presided over the longest period of continuous peace in Rome's history. It was a golden age for Rome in which the economy, the arts and the welfare of the people flourished like no other time. They said of him that he found Rome a city of clay and left it a city of marble. The man was a genius of the highest order and possibly the smartest man ever to rule any nation.

Not everything in a leader is military accomplishments, but Augustus does have those, too, defeating Mark Antony in a civil war that ended at the battle of Actium.

He was an all-around man of high accomplishment with few, if any true failures.