Here's the thing, as far as villains go and their threat levels:
-Lex: City-wide threat; anything global is honestly above him. Potentially threat to Superman, but usually through other means (like Metallo).
Lex Luthor, who managed to become President of the United States in the comics can't be a global threat? Seriously? Oh well, I've never been a big fan of Lex as anything but an instigator of trouble, and I don't think we need another Superman movie with him as the villain.
-Brainiac: City-wide threat if going with the \"bottling cities\" but could easily be a great planet-wide threat. Potential threat to Superman, ESPECIALLY if you use Brainiac's origin from the Animated Series and have him be the Kryptonian council's AI. Goddamn, that was brilliant.
Planet-wide threat if it's a version of Brainiac where he destroys whole planets after analyzing them.
Personally, I say forget a Superman movie, and go with the Justice League versus Vandal Savage. No origin story, either. I don't want the Justice League forming to take down a surprised Vandal Savage. There have been how many blockbuster superhero movies in the last decade? After a half-dozen franchises, I think audiences can handle the concept of "there are heroes with amazing powers who fight bad guys" without having to spell it all out. I want Savage to have been planning the destruction of a well-established League for a long time. Let the take-down of each member of the League tell the audience what they need to know about who they are.
Though, if we are going with a Superman movie. My Top 5 Villains Who Shouldn't be in the Movie:
1. Conduit
2. Hank Henshaw / Cyborg Superman
3. Momentus
4. Solaris
5. Mammoth
I'm trying to think who I would want to see.
- Mongul is a great villain, but taking the action to War World for a reboot kind of removes the Superman as Earth's protector angle, which is pretty important.
- Darkseid is, possibly, too powerful. While I think that an origin story is unecessary for a reboot, I think it's still necessary to establish Superman's power level before having him trounced by a demi-god. That was a problem in season one of the Justice League animated series. They tried to establish how powerful the villains were by having them take out Superman, and ended up making Supes look weak, instead.
Maybe if Superman really feels on top of things before Darkseid starts an invasion in earnest... Hmm, that could work. Darkseid is, as ever, searching for the anti-life equation, and has really only sent a scouting party to Earth. Superman is taking some blows, but is still prevailing against some pretty titanic forces sent by Darkseid. Then Darkseid has reason to believe that what's he's looking for actually is on earth, and the flood of troops begins. Overwhelming odds make Superman question his tactics, and then Darkseid shows up in person to make Superman question himself. Then we get:
Or something really close, when Superman realizes he can cut loose. Instead of Darkseid's strength making Superman look weak, the challenge of Darkseid shows just how vast Superman's limits are.