While Hitler can be admired for many of his abilities, such as public speaking and swaying the masses...as well as for many "good" things that he did for the people of Germany....he was no great military commander. That was one of the reasons things started to go so badly for the Nazis during the second world war. They began to loose so much ground so quickly because he refused to listen to his more experienced generals. So, yes...he was very successful early on, but too pig headed to listen to reality when his plans started to fail. He simply wouldn't listen to those people who knew what they were talking about.
Thutmoses IV -Very great Egyptian pharaoh. Expanded the borders of Egypt into a huge empire. (I would say Ramses the Great as well, but he was better at propaganda than actual...warrioring -if that can be used as a term)
Caesar -duh
Alexander the Great -Obvious
Napoleon -again, obvious
Washington -Along with LaFayette, he turned a band of poorly trained rebels into a successful fighting force. I mean, when you get right down to it, he was the one behind the idea of actually getting out of the way of a bullet when it was coming at you, rather than marching in formation onto the end of a bayonette. He changed the rules of warfare for so much of the western world.
FDR and his generals -He actually listened to his people. This was one of the reasons why the allies began to win.