10-11
What other lists of world leaders can people name? I can name every head of government of South Africa, both prime ministers and presidents. It's a neat party trick. I can also name all the Fifth Republic presidents of France, but that's not difficult.
All Presidents of the French Republic
Emperors of Russia and subsquent Soviet and Russian Leaders
South African leaders (yes, Xahar, that's a neat party trick indeed)
Rulers of Poland
Presidents of Poland
(almost) all Prime Ministers of Poland
Chancellors of Germany
Presidents of Brazil
Prime Ministers under the Fourth and Fifth Republics (there's no way I'm memorazing the Third Republic
)
Prime Ministers of the United Kingdom since mid-19th Century
Presidents of Iraq
Also some very short lists as PRC Leaders, Presidents of Egypt, UN Secretaries General etc.
A better question is if you can name all 100 Senators?
Yep. Governors as well.