I think the way to describe the “best” narrative – that is, the narrative that, regardless of its content, is the most structurally-sound, streamlined, well-put-together – is that it is both unexpected and inevitable. While watching it, you can’t predict the outcomes of the events you’re seeing onscreen, but once you’ve seen it and you look back on it, you realize that it couldn’t possibly have happened any other way.
What I think is interesting about this is that it seems to describe two different modes of appreciating a movie, so what I’m going to do is assume that this is (as it intuitively seems) a correct assertion, and proceed from that to elucidate what I think are the two fundamental elements of narrative. Some of this is going to seem pretty obvious, but just because a thing is obvious doesn’t mean it isn’t worth exploring a little bit.
Those two elements are Plot and Story.