Let me first say that Hitler was mad and evil to the core.
He was, however, a political genious and Germany benefitted greatly from his leadership. Now before I get flamed, let me explain further.
The German people wouldn't have followed Hitler if they were not in a hopeless situation! The Treaty of Versailles left Germany in an oppressive situation, which added to it's wartorn economy after WW1, that was unjust. While most of the advanced economies collapsed in 1929, Germany's economy had been in depression since the end of WW1. Enter Hitler. He began turning Germany's economy around in the mid 30's. Many major projects, such as the Autobahn, were began and Germany finally began to recover. Many of these beneficial projects were in contravention of the Treaty, especially the developement of the aircraft industry, which probably helped in making the Germans more eager for war. Soon despair turned to pride, then pride to revenge! Without the Treaty of Versaille, Hitler would never have had the power that he did.
Does this make Hitler a hero? No, what he did was inexcuseable. What it shows is that when dealing with nations, one needs to be careful not to be too oppressive. I'm concerned that we may be making the same mistake with Iraq and Serbia, we should probably assasinate or kidnap Hussein and Milosevic so that the people of those countries can get on with their lives, not having us Allies bombing them every so often.
After WW2 the error of the Treaty wasn't repeated. Germany and Japan were aided economically and have been peaceful since. Kinda shows the wisdom of turning an enemy into a friend.