Is there anything that determines whenever a ruling monarch is a count, marquis, duke, archduke, prince, king, or anything else ?
Tradition. Entirely tradition.
Wikipedia has a page on every royal title, which also includes the note:
Several ranks were widely used (for more than a thousand years in Europe alone) for both sovereign rulers and non-sovereigns. Additional knowledge about the territory and historic period is required to know whether the rank holder was a sovereign or non-sovereign.
It's also complicated by the fact that titles in different languages don't necessarily have direct equivalents in others. Tsar is a great example: It comes from the Latin caesar, but there is no modern English title that derives from caesar. I think it's usually matched to "Emperor" when it's not used as-is, but that comes from the Latin imperator.
Looking it over, my impression is that whether you were a Prince, Duke, King or Emperor (or their local equivalents) depended on how big the territory you claimed was (in ascending order). If you were first among relative equals, you might be a Grand Prince, Grand Duke/Archduke, or King of Kings.
Wikipedia also has a list of the remaining sovereign monarchs and their titles, which include Kings, Queens, Princes, Grand Dukes, Sultans, and Emirs (and a few others).