Once upon a time there was a movie called E.T. The Extra-Terrestrial was a great story and a great movie. Along with it came tons of great merchandise. Most of you played with it.
There was also an E.T. game for the Atari 2600. Think back! Did you ever play that game? You didn't? The story goes that very few did play the game and that the company buried millions of game cartridges in the Mojave dessert. This story is now urban legend, but it is not urban legend that almost 30 years later, movie-based games still suck.
I can think of one main reason. (Can think of several more:-)
In films as well as games, you act as a God creating a world. However, you act as two different kinds of God.
In a film, you are the dictatorial God. You decide everything. What is said, done and shown to the audience. In games, you are the initiating God. You create the world, the boundaries and the rules of the world, but it is up to the audience to enter the world and interact to make the world complete. A Film can be shown without an audience to an empty theatre. A game cannot be played without at least one player.
I think that most of the key people in Hollywood don't understand this profound difference.
Why do you think that most movie-based games still suck?