The Sta-Puff Marshmallow Man!
That way, one could literally sing…
♫"It’s a marshmallow world…"♫
Who doesn’t want to live in a marshmallow world?
Galactus doesn’t eat humans. We wouldn’t even have a place to live under, as he wants to eat the earth.
You all need re-Neducated!
I didn’t know Hank Scorpio was a villian. I mean I liked the guy.
Dr. Evil. The only downside would we’d have to listen to that schtick over and over again ad nauseum. So, there’d be no difference, really.
It might be fun if Mr. Nobody and the Brotherhood of Dada were running things.
Uh…
Doom Patrol…
Hello? Anyone?
Nevermind, it’s not like a tree fish toilet in the afternoon. I know-- I was there, and the opera was far too orange.
I think Vetinari is a good example of a villian who’s made it. If he was slightly different he’d be a real villian, but as he is, he runs a city as well as possible.
Just don’t be a mime artist 
Now do you mean supervillains who actually could take over, or someone like, say, Two-Face, who couldn’t even if he wanted to? Are we talking credible conquerors or Joe Supervillian?
I wonder what life under the Purple Man would be like? Probably pretty much the same, unless you ran into him.
“Taking over the world is one thing. Finding good help to run it is another.”
Anarchy, the teen supergenius from the Batman comics, wants to eliminate all central authority and establish a sort of Heinleinian libertarian utopia. Be one hell of an interesting experiment if nothing else.
Well, he threatened the UN and aimed a giant laser at france. Make of that what you will.
I’m not seeing a problem. 
Scorpio: “Bye the way Homer, what’s your least favorite country, Italy or France?”
Homer: “Uh…France”
Scorpio: “Ha, Ha! Nobody ever says Italy”
Didn’t he not fire it, though?
He also blew up a bridge outside the UN. And killed James Bond. And roasted a whole bunch of soldiers with a flame-thrower.
But he was a great boss.
Yes, but did he do anything evil? 
Another vote for Pinky and the Brain. The Brain might get his jollies by making us run through pointless mazes now and then, but otherwise he’s not a bad guy, as evil genii go.
As for Dr. Who villains, what about the Master? He says he wants to rule the universe benevolently – let’s see if he can back it up!
The Antichrist would be interesting (in the Chinese sense) – and it would be so wonderful to be free of all those raptured Christians! – but there’s no stability under his reign. The Four Horsemen run amok, the price of food goes up, and so on, and so on, and the whole thing only lasts a few years anyway, until Jesus comes back and spoils all the fun.
Doctor Sivana from the old Captain Marvel comix was obsessed with becoming “rightful ruler of the universe” – until that day he was content, most of the time, with being a prankster, spreading malicious mischief with his horrible machines. But he was one hell of an inventor! Maybe if we put him in charge, he could solve all our problems! Cold fusion, cancer cures, FTL travel, you name it! Then again, Doctor Doom is an even better inventor.
I think I’m going with Hank Scorpio too.
Old Luthor – pre-Crisis/pre-70’s Luthor once was hailed as a hero and brilliant, laudable leader of an entire planet. He cured disease and created a society in which everyone had plenty. He had the advantage that the aliens weren’t humans, but I think if he weren’t obsessing about Superman, he’d create a tremendous world to live in.
Darth Nader
I prefer the second incarnation of the Brotherhood. It was during that time that Mr Nobody launched his bid to take over the USA, by being elected president.
“Art for breakfast! Art for lunch! Nobody for president!”
ddgryphon
Although briefly happy as benevolent ruler of Lexor, Lex could not restrain his urge to do evil. He began committing crimes in a somnabulist state.
Actually, since Galactus wants to eat the whole earth, he probably thinks of humans as jimmies – which is probably why some of us are named “jimmy”.
Um, which Bond film was it where Sophie Marceau (gorgeous french actress) tied James up?
Because that’s a world I could get used to… 