Concept was pretty standard I suppose. Introduce Danny and his friends/family/community. Emphasize on how hard his life sucks. Vlad Masters comes over to help the Fentons build their portal and comes across as a really good guy. Danny turns on the portal and gets his powers just before breaking it. He pretty much uses them to get back at people who made his life miserable and have fun with his friends. He saves a group of hostages and realizes that it might be fun being a superhero as well. The media dubs him "Inviso-Bill"
Vlad learns of Danny's new persona and reveals his twisted plan. Not only did he plan on using the portal to unleash physical manifestations of ghosts into the world, but to rule both realms and--double shocker-- his plan was too use the Portal to give Maddie ghost powers and knock off Jack. Long story short, Vlad unleashes a ton of Ghosts onto the world, Danny has to save everybody, Vlad is destroyed (or is he?) and the movie basically ends with Danny having saved the world from Vlad but continues having to capture and send back ghosts i.e. Reaper or Ghost Rider.
A couple of points I wanted to make, I really wanted to make Danny's life suck between the embarassing family, bullies, a-hole principal and shallow romantic interest.
I want Danny Phantom and all the ghosts to be motion captured CGI in a live action world since it has a quality where it looks human and yet is fluid and frighteningly unnatural.