Actually, the South has won the battle of history. "The Birth Of the Nation" and "Gone With the Wind" sealed the deal. True, it's not popularly called the War of Northern Aggression, but for generations the cause of the war -- the continuation and geographic expansion of slavery -- was obscured by arguments about states rights. Just this past week our President made statements minimizing the importance of slavery in the conflict. To this day there are more U.S. military bases named after confederate leaders than Northern generals.
Genghis Khan is generally considered the worst mass killer in history, but Caesar's Gaul campaigns probably put him over the 1 million killed milestone. I don't know for a fact, but as a percentage of the population that may actually put him "ahead" of the big league 20th century tyrants.
How come Emperor Hirohito gets a pass. Military deaths, war crimes and starvation in the Pacific/SE Asia war area approach 10 million and that doesn't include their actions in China.