Johnny Novgorod said:
I didn't mind Prometheus but... what's the point of these movies? We already know all there is to know about the alien. You get to experience all the awe and wonder and fear in the first movie, and every other movie builds on that mythology. What's the point of a prequel? Why do we care about the alien's origins? When have we ever cared about the origins of something that is established with a cool mystique, like Bobba Fett?
I agree. An implied back story is just a bit of flavour to help flesh a character out. They aren't designed to be expanded into exciting, grand stories in their own right, otherwise the writers would have started with
that story first. For example, Obi Wan mentions he fought in the clone wars with Luke Skywalker's dad. It was just an inconsequential detail used to explain how this old man knew Skywalker senior, but it ended up leading to a three movie prequel series that inevitably spoil the big twists built into the original trilogy.
Alien doesn't need a prequel to explain the Space Jockeys, they were just a damn plot device.