There are a few ideas rehashed over and over, and some of them go a loooong way back (one reason why stories of other cultures are interesting - they have other patterns). Forbidden love, son-father relationships, coming-of-age, ... (look at Star Wars and find those, for example)
If you take care, you can probably predict the storyline for most movies as you go along, save for a few variations the themes have (so you'd have to predict for two storylines and guess which one it is going to be). It is a human ability, really, that builds our societies when we agree on what can happen. And most people seem to like this kind of storytelling. It's rare to find new ideas.
Just some thoughts. </rant>