Which ones have lasted, or still have the most influence?
China (longevity/population)
India (longevity/population)
Spain (cultural influence in Americas)
Britain (cutural influence/global reach)
Arabia (cultural influence/global reach)
I don't think it can be limited to just five though; I'd add a second division to the premier league:
Mongols (virtually everyone in Asia can claim to be related to Genghis)
Rome/Greece (cultural influences on later empires)
Egypt (longevity)
Persia (longevity)
Germany (longevity)
Russia (global reach)
Then there are the civs that are culturally distinctive for one reason or another: Aztecs/Incas, Japan, Ottomans, Vikings, Mali etc. I reckon America is too recent to judge properly (and in the long run, may count as an offshoot/successor to Britain... not that I want a barrage of flames from outraged Americans over this statement!)
I think there's plenty of room for more... Even the French.
