Movie 6 and Movie 11 definitely. For animated films, those two kept me excited and left me wanting more when they ended.
Though in Movie 11's case, it might have something to do with my love for Sonoko since she does have a bigger role there.
I also like 4,5,8,10 and 12.
13 bored me for some reason. And 14's plot was just plain idiotic imo.