Well I'd go for story structure. Cos that's what u think about after the movie. Also a gd story structure shows the directors' train of thoughts. No use having star-studded stars if the directors can't think clearly imho. The message gets lost in the act.
Special effects leh. Er yea they're good. But if they're used for the sake of it, u end up feeling empty after the movie.
I like to see how they set the camera angle, how they set the light & lighting, of course if there is a strong and original story that helps. But a good story with poor camera skill will make me shiver sometimes.