Movie fails

Rating: 4/10 (8 June 2012)

********** S P O I L E R **********
I just came home from the movie theater where i saw Prometheus. Overall it was a good movie with a few awesome 3D effects. But i still left the movie theater with a feeling of frustration because of the ending. The whole foundation of the movie was that these Engineers supposedly created mankind, but now we found out that they had started creating weapons of mass destruction and planned an attack against earth. A good story in itself. The frustrating part was that we never got to find out what was behind this decision to destroy earth. Why were the Engineers so disappointed with their human creation that it drove them to wanting to obliterate the entire species of mankind? Where did the writers of the movie hide the back-story for this? Sure, it's up to each viewer to interpret this, but i want the view from the creators of the movie, what did they have in mind by letting this movie go the way it did?
I'm comparing the ending of this movie with how it would have looked like if "Lord Of The Rings: Return Of The King" had ended with Frodo standing on the edge with the ring, without letting us know whether he threw it in the flames or not. This isn't what we want, we wanna see that he threw the ring into the flames. And i wanna know the background story as to why human kind as a creation had to be eliminated. Not based on everyone's own theories, but by the creators of this movie showing us. That's why Prometheus feels like a fail in my opinion, a good movie that is ruined by a bad ending.
If they're planning a Prometheus 2, perhaps as a prequel where we get to see the Engineers planning and their motive for why human kind should be eliminated, then i can accept this movie as a nice piece of work. But if it ends like this, it's just a fail.