It's no use trying to make a sequel fit better with young boys/men. Spider-Man did not do better because of a supervillain. It did better because it had Kirsten Dunst and Tobey Maguire with great chemistry and a lovestory that connected and made this to be the movie wich girls and couples choose to see.
If one take a girl to the cinema today, the smart thing would be to take here and se POC2, because that is a movie which fits the profile better. And a supervillain would not change that at all.
But a better casting for Lois or a better lovestory would. There is a reason Batman begins did not go past 204 million, because no matter how brilliant it was it sucked when coming to the lovestory, mainly because of a terrible Katie Holmes.
Don't get me wrong, it would be cool to have Superman bleed or put in a supervillain to have Superman fight. But if one thinks that will make the movie a bigger box office hit then Superman Returns, then I'd suggest one to think again.
With a concept like that the most the movie could hope for will be 250 million, and then it has to be freakin awesome. Make it connect with the female audience and the sky is the limit.
As for story arc, I could care less for a supervillainfight. That would be cool, but I'd much rather see something like this:
Middleast. A building is crushed after a missile strikes. The israeli are repelling a terrorist attack at a large scale. A young palestinian man is crawling through the destroyed buildings, he sees friends and fellow soldiers lying dead on the ground.
Around the corner an Israeli tank is approaching. The palestinian boy takes the rocketlauncher and aims. He can see the face of the soon to be dead Israel soldier who's head sticks up from the giant tank. The palestinian boy fires, for the first time he will take a life, he thinks. But then, out of the sky the rocket is grabbed by Superman. He looks at the boy with a harsh looks. He takes the rocket and throws it out of the atmosphere.
The tank closes in. Superman lands in front of it. "This ends here" he says. The tank stops, Superman aproaches, he places one fot on in at steps up so hard that it is crushed under his feet. With his hand he bends the canon.
Speaking israeli he says:
"no more killing today. You might want to fight the palestinians. And they might want to fight you. But you should ask yourself; Do you really want to fight me?"
Apart from my bad writing, basicly I want to se our world with the impact of Superman. I want to see Superman guid us and show us the way
And in comes Brainiac....