Thus ends the advertising portion of this review. From here on out, I will fairly well spoil the entire movie. Please refrain from reading any further if you wish to stay unspoiled. For the sake of not recapping the entire movie, I will write as if the reader has already seen it.
The movie can best be explained as a series of increasingly complex questions that relate to creation, destruction, and the nature of life in general. The opening scene we see a humanoid alien with seemingly perfect physical features perform some sort of ceremony where he drinks liquid. Soon after, this liquid disintegrates him on a genetic level, making one wonder, was such an act intentional? My conclusion, based on evidence from later in the movie, was that it was not.
For a good chunk of the movie thereafter, we are only given hints about who this alien was, what his intentions were, and what the liquid actually was. To be honest, we are never given any real concrete answers to some those questions, but we are given clues.
As to who the alien was, it was quite obviously a member of a race of beings that intended on creating life, and succeeded. What their goals were in this creation are unclear, but it is obvious that they got quite good at it, seeing as they were revealed to be the originators of the human race. Perhaps, then, this ritual he performs is the initiation of that process; he drinks the liquid, and that, in some way, allows a genetically similar, mutated species to form. This scene, then, is the explanation of how they create life.
What must follow, given that they were the creators of the human race is, why would they change their minds and decide to eradicate us? Were they afraid of the human race's potential? If we take the parallel between the humans creating androids and the aliens creating humans, perhaps it is true. The actions of the film's android, David, and his line, "Doesn't everyone want their parents dead?" give away his intentions of turning on his creators. The aliens, then, could have been acting in advance of such a turn in the mind of humans, deciding to kill them before they could develop enough to become a threat.
Perhaps it is simply an exercise of power over their own creations. As the cliche goes, they gave us life, and they can take it away. These aliens could be playing God, creating life and destroying it with the same tool that they discovered. Only at some point it backfires, and that is where the Alien xenomorph comes from.
Of course, this is all guessing, and the whole thing was written with a sequel in mind, but I would like to hear other people's thoughts nonetheless. What do you think?