The Terminator franchise is an excellent example on how to turn a terrible concept into a fantastic movie by just using good writing and directing. The story is about a computer called skynet, sending a robot back in time to kill the mother of the child that will basically destroy skynet by starting and leading a rebellion against skynet's genocide of the human race. It sounds like the story of a cheesy Saturday morning cartoon. So many things could have gone wrong but James Cameron pulled off a believable, dark, exciting movie by using good acting, casting, cinematography, writing, and special effects. A lot of people defend the prequels because they say it was hard material to work with, but really the material has very little to do with the effectiveness of the movie. You could make a movie about a bunch of people in a room and depending on how you write direct and film it it could potentially be a very interesting and entertaining film.