How would a King Of The Hill movie work? I mean, you couldn't really come up with a good plot for it that hasn't already been used, and it'd get old after the length of a normal episode.
Family Guy wouldn't work because it'd go overboard with the cutaways which would get old after a while, and if there weren't as many, than the fans would be disappointed, and you'd release the fact that the show can't hold itself on it's own without the cutaways. And the writers would go overboard with an R rating, losing a good deal of it's audience.
American Dad might work, but not many people would go see it anyway.
Futurama, by default, would be the best bet, but probably woudln't keep a good plot for 90+ minutes.