@ yarb: Don't forget the Daisy Dukes. They tend to rank somewhat higher even than marquises, because that's how high the hems are.
@ logos: by that token, the JMU Dukes could conceivably be the Maddies, which is far less intimidating, while any Dukes of Hell could conceivably be the Hellies... Hmm. Perhaps this could be the start of a trend of re-naming sports teams? I vote for the Pittsburgh Burgies. :)
Wait. It doesn't work for the Dukes of Hazzard. The Hazzardies just sounds goofy.
On the other hand, it certainly works very well for the Duke of Wellington.
Yarb, a count is generally the continental term for what the English called an earl, so those two have relatively equal ranking. They rank higher than knights or chevaliers.
Dukes are not always the sons of kings. In fact in most cases they are not, though a duke is of higher rank than count/earl. It's usually the highest rank under the monarch; there aren't a lot of hereditary marquises.
Marquis is higher yet than a duke, and there are far fewer of them (female version I think is marquise, though I always want to think of a marquess as being female). The titles tend not to be as hereditary as, say, that of an earl or duke. (Though in all honesty I'm not sure what "as hereditary as" could possibly mean legally.)
However, you'll recall that whichbe called this demon a Grand Count. That's presumably of a higher ranking than your ordinary, run-of-the-mill street count. Still, I would suspect that a Grand Count is still not higher than a duke, and then you also have Grand Dukes, Archdukes, and so forth.
Which reminds me of the Onion headline of August 1914: "Assassination of Archduke Spreads Fear at Archduke Convention."
I think the google stats could merely show the general belief that counts are of little import compared to earls (especially if you consider the Duke of Earl, a very popular song indeed) or dukes. If the Sumerian demon weren't such a gentile-dispositioned demon, perhaps he'd insist on being ranked the Grand Archduke of Hell. Though, in that case, I'd recommend he change his name, in keeping with his new station, to something considerably longer and less pronounceable. As would befit a Grand Archduke of Hell.