Napoleon's was largely a European + Mediterranean. I don't think there has ever been a true world war, to be honest. Even WWII didn't include South America, at least not that I know of.

Umeu: The Mongols didn't conquer Asia, at least not the whole of it. No single state has ever controlled a whole continent, apart from Britain controlling Australasia, and perhaps anyone who first claimed the barren wasteland of Antarctica.