This post will still contain spoilers. I will summarize my base feelings at the end (set outside the dashes).
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Ok. The movie has a lot of interesting concepts introduced, leaving only a few questions, really.
First: Why create the humans?
Answer: No clue on this one. The love interest, in a conversation with David, explains that humans made androids because they could. So far, this is the only suggest answer we have.
Second: Why kill them off?
Answer: Got nothing here. Maybe they were working on making biological weapons and the human batch weren't up to snuff. The new alien soup was more what they wanted, maybe.
Third: Why would there be cave paintings pointing to the planet we see? It isn't a homeworld, it is a storage planet for ships carrying the goop.
Answer: Maybe because that's where the goop came from and the goop or first alien remembered it somehow. Can't say, seems a bit like a plothole to me.
Fourth: What happens to the lead female's ship after the end?
Answer: Possibly, it is the ship found in the first Alien movie. The planet in Alien is NOT the planet in Prometheus. Something could go wrong, causing the ship to crash. This will probably be the ending of the sequel, should there be one.
Note: an Engineer's suit is shown in the Alien film, sitting in the pilot seat. Being that it isn't know that this is a suit, I propose that anything could be inside and the characters from Alien would never noticed -- either David or the female lead could actually be in the suit at that time, if it is the same ship.
(Art of the Engineer's suit from Alien. This character was known as the "Space Jockey")
A lot of the designs in the movie are obviously echoed in the xenomorph architecture seen later. This was done well, I think.
As to the evolution of the alien soup, I'm not sure how I feel about it. In this films, it seems very pliable, always taking a dramatically new shape. The xenomorphs are more of a finished product, though they also adapt depending on their host bodies. I suppose it makes sense that the xenomorphs slow down their evolution if they are the final product, or the most viable mutation the soup recognized. That would fit in with humanity being made from a similar goop that evolved from different shapes over time.
Making that connection makes me like the alien evolution more, actually.
Final interesting note: Peter Weyland's motives/character are done well, I feel. He represented a base form of greed that is always present when "the Corporation" in later films/works are noted. It makes sense if they were also following a directive put in place by Peter.
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Did I like the film? I think so. I found certain points (the snake/lamprey throat entry and the Cesarean Section in particular) disturbing. I'm not particularly easily disturbed, but the snake/lamprey thing was slimy and nasty and reminded me of a leech or a slug. The Cthulhu head was just damn disgusting.
I think the pacing was done well. It starts slow but picks up pace 3/4ths of the way through. And the suspenseful moments actually feel intense -- several instances I heard the audience around me letting out held breath when certain scenes ended.
As a prequel to the Alien movies, it also works. It's missing a Prometheus 2 link, but, even if one is never made, certain things can be inferred. Having seen the movies and read different Alien novels/comic books, I appreciated finally seeing the origin story they told. Also, finding out what the Space Jockey was was also interesting. It conflicts with some comic book material, but the movie trumps them in the canon department.
Cast/Acting was done well, if not focused on too much. Plausible action sequences and general sequence of events are almost all good.
Yes, if I had to give an answer, I enjoyed the film. That being said, I do not think I will ever watch it again. I may go back and re-watch Alien, Aliens, Aliens 3, and Alien Resurrection, but I don't think I'll ever have the desire to watch Prometheus again.
If you are a fan of the series, the movie is a definite GO. If you are a fan of suspense, I'd say it's still a go, though I suggest you watch the Alien series beforehand -- without it, you miss out the importance of certain things. If you're note a fan of the series, suspense, or Sci-Fi in general, I'd skip it. It's not gory enough to hit the gore fans, just enough to upset me.
I'm going to go have nightmares now, goodnight!