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I wish it were that simple.

The Byzantines for instance didn't quite have titles in the feudal sense (not really). They had a bureaucracy. Plenty of nepotism and nearly-hereditary stuff, but nothing like the West European "King-Duke-Count-Baron" system.

Russia is a different kettle of fish altogether. Both Duke and Prince were interchangeable (it doesn't translate precisely into English, where we are influenced by the British system, which is in turn different slightly from the Continent).

Here's a link to Wikipedia's main page for noble titles:

Wikipedia on Titles and Stuff
 
Unless you mean specifically what titles are in CK, but I can't imagine that... since having that game the answer is already there :)

Orthodox: King-Prince-Count
Catholic: King-Duke-Count

There has only been one Archduke that I know of, that of Austria. "Lord" isn't a title, and Grand Duke depends on language. Knyaz in Russian, which is where it most frequently appears (knyaz is also translated as Prince).