Nothing at all. When - not if, but WHEN - I am the unquestioned lord and master of Earth, my name alone shall be all the title I need. Titles are tools with which to remind those you command that you command them - but when I command all, I hardly think such tools shall be necessary.
Of course, “Arbiter” would be kinda badass.
Caesar
Archon Belisarius
Or, on a more modern note…
Big Brother.
“Sir”. 
Well I like Supreme Goddess myself, it was a self-imposed nickname in high school, but that is so eighties now.
How about “your highnessty.” Or would it be spelled highnesty? I’ve always liked the sound of that.
Perfect Master has a nice ring to it, I think.
Hmmm
since I would rename the world LennyLand
I would keep the name Lenny!
all my ministers would also be named Lenny.Len or Leonard.
such a underused name
Pontifex. As in Qadgop the Pontifex.
Dearest.
Also:
Destrovator.
The Prophet.
Bwana Dik.
Sweet Highness of All That is Worthy
Mr. Excellent would be good, but since it’s someone else’s name here I’ll go with… The Enlightened Perfect Master.
What about those of us who burst out in a fit of uncontrollable laughter?
Lolth… snicker
Most Beloved Empress of the People or Our Serene Lady of the Light.
Guided by countless S/F novels as a child, I’d probably go with something along the lines of Supreme Terran Chancellor. Simple and to the point, and fits nicely on an embroidered polo shirt.
Maybe Charter Member.
DRAGONLORD
I was born in the year of the Dragon.
Sun Tzus’s ART OF WAR will be required reading in school. Passing accounting will be mandatory for graduating from highschool.
Dal Timgar
Feuhrer
The Grand Puhba of Scrumtralecense
Great One
or just plain HIM!
This is a good thread. It gives you all a chance to practice addressing your future ruler. It is important to address me correctly, or else you’ll be taken out and shot…er…I mean…a…sent to happy, fun, non-purging camps (this is why I’ll be ruler).
I’d cook up a ridiculously long list of titles, and force the entire popluation to memorize all of them. Whoever refused, or changed some of the titles would be slowly whipped to death with scented bootlaces. (Shamelessly stolen from Terry Pratchett in one of his earliest Discworld books)
Praetor.
It’s an old Roman title, not one of particular power so far as I know, but I like how it looks and how it sounds. Plus, it’s the title of the sovereign of the Romulan Star Empire and since I’m such a Rihannsu fanboy, I would want that to be my title.
Beneficent Maternal Protector, Kind Leader and Arbiter of Good Taste 