Roger Ebert liked to quote Howard Hawks' definition of a good movie as "three great scenes and no bad scenes." (He does it in this review, for instance: www.rogerebert.com/reviews/grea...)
Also film is a visual medium, I love a terrific plot but plot is definitely not needed for a great movie.
Saw someone say "good scenes don't equal a good story." Foolishness. BATMAN is a borderline unwatchable movie outside of five all-timer scenes (imo), but it HAS those scenes and is rightfully considered a genre classic. Plot structure matters, sure, but five good scenes can carry the whole boat.