Aelia is right, Gaius Julius was a lot on the road with his troops. He completely conquered Gaul, expanding the Empires boundries all the way to the Atlantic ocean. And btw...it wasn't an empire before he came along, it was a republic, with squabbling senators and backstabbing upperclass citizens.
Furthermore he conquered Alexandria, parts of North Africa, and Iberia. He was also responsible for the first Roman invasions in Britannia in 55 BC.
Gaius Julius Caesar deserves more to be on that list than most who names i see, especially Hitler. Not one time did he lead an army into battle, and he became more notorious because of his tactical blunders than his military genius.
Oh...before i forget...
http://en.wikipedia.org/wiki/Julius_Caesar