The only reason why im saying this is because of the cameo will he apear again if he does who will voice act him and will he make Ultimate Spider-Man better since these 2 sorta have the same personlity.

I really hope he does. I stopped watching this series months ago, but I would come back for Deadpool xD Hopefully they'd get Nolan North to voice him. I don't know what they're actually going to do though :0

Probably. Seeing as how popular Deadpool is now with kids, I think that an appearance in Ultimate Spider-Man is pretty inevitable at this point. It would also work seeing as the show is really comedic. Deadpool would probably get his own flashbacks/daydream sequences.

I'm not sure whether he'd be a villain or an ally; Probably start off as the former then end up being the latter. You're right, though. They do have similar personalities. One would have to take a backseat to the other in terms of goofing off/wise cracks. Usually when the 2 meet in the comics, Spidey plays the straight man, but I doubt they would change his personality much.

He was supposed to appear in Wolverine and the X Men, and while I'm sure they'd never give him a series (it would either suck or get cancelled after 1 season) I could see him being a recurring character if they ever gave Wolverine a show.

It'd be hard to pull off a Deadpool friendly enough for kids......
 
Although I suppose if they did it like the Deadpool in Shattered Dimensions it could work. A TV host who is running a dangerous game show, and puts Spider-man on it to boost ratings. It would make sense, what with him being on the cover of a magazine in one episode and a character in a video-game in another episode.