That's a tough call, I don't think I could pick one overall favorite. There's several choices coming to mind, so here they are in no particular order: -Anything by Hayao Miyazaki -Paprika -Cowboy Bebop: Knockin' on Heavens Door -Macross: Do You Remember Love?
Honestly I'd probably pick Macross: Do you Remember Love? simply because it's probably the best animated movie of all time, but all the others are really close for me.
I guess you are right, there is a Family Guy movie... it sort of went straight to DVD so I never counted it. The Simpsons you could see in theatres. I want Family Guy to hit the theatres. It was better than The Simpsons so if I am going to count a straight to DVD then I change my answer to Family Guy. "Family Guy is funny..."