A nice mix of difficult and not so difficult. There were some I was proud to get and those 5 I missed I would never have gotten. (Aztec, Persian, British, Islamic and Maurya)
Maybe include some Japanese emperor? Gustav Vasa of Sweden is also one to think of though not as great as some of these. A Viking like Bluetooth/Blåtand?
Though I think pretty much all of the Japanese emperors most people have ever heard of are already included in my 19th Century World Leaders quiz and my World Leaders of the World Wars quiz. Those being Meiji and Hirohito. If I used any from before 1800 I'm guessing they would be guesses about 0% of the time.
Apparently I just skipped over the Peter the Great question. I would have gotten that one. I must have tried spelling Nebudchadnezzar ten different ways before finally giving up. Too bad I didn't try spelling it H-a-m-m-u-r-a-b-i.
I think I'll expand this soon and probably add Hammurabi. Some other potential additions: Solomon, Xerxes, Nefertiti, Ramses, Hatsheput, Kublai, Richard, Qin Shi Huang, Bluetooth...
Maybe you should accept Friedrich and not only Frederick - that was his actual name, after all :) There are some others with alternative spellings such as Hammurapi/Hammurabi
Maybe include some Japanese emperor? Gustav Vasa of Sweden is also one to think of though not as great as some of these. A Viking like Bluetooth/Blåtand?