Here are a few things that I love: Ridley Scott, Alien, movies with lots of themes, movies that are maybe too big for their britches. So let it be known I'm not really coming from a place of impartiality regarding Prometheus.
That said, apparently a very large number of people hated this movie. I am not one of those. Having seen several non-spoilery remarks of loathing beforehand, some from people whose taste I trust, I was prepared to be disappointed--and came out quite glad that I was not. Since it IS partially a horror film, most of the characters, despite being scientists, are too stupid to live (particularly the main male archaeologist, who was also a total asshole and deserved to get Alien'd), but that's how horror films function and I don't think it's a very significant complaint, especially given how many of the "too stupid to live" actions are rooted in the film's ever-quest to gain knowledge. People will do extremely idiotic things to get answers. That is the story of (cinema) history. Other complaints are that the film is too steeped in Greek and Christian mythology to be digestible to the average viewer, a complaint that I totally can't get behind because I enjoy films that make me consider what I already know, force me to bring my own interpretations and lens to the viewing, and aren't catering to the lowest common denominator. If Prometheus made someone go out and get a book of Greek myths (or better yet, a book of world mythology, since a lot of the patterns and tropes used in the film are cross-cultural), so much the better. The third and most prevalent complaint is that the film gives no answers and that this is a cop-out.
Now, as someone who utterly loathed the LOST finale, I can kind of understand where these people are coming from. Damon Lindelof co-wrote the Prometheus script and it does show. But for me, two hours of film in an established universe is a completely and significantly different medium and vehicle of storytelling than six seasons of character development on a network television show. And for me, the major overarching theme of the film was that sometimes the answer is infinitely less interesting than the question. Would all the people who disliked this film as it stands be satisfied with it if the answers to The Big Questions asked throughout had been provided? I would have found that an entirely unsatisfying film, because the Alien franchise is not and has never been a monster-of-the-week affair. There are many kinds of science fiction, and Prometheus and the other Alien films reside in a universe which wants you to think it's ours, and not in the same way that Firefly or Stargate SG1 does. Here's where I go my usual route and turn to heavy metal lyrics. In the Kamelot song "The Edge of Paradise," the chorus states: "Undermining life itself/my will to wonder why"; in the Conception song "Cardinal Sin," there's the line "tell me that it's worthwhile/to get behind the why/where all is true." Both of these encapsulate the fundamental human search for understanding, and more than that, they really hammer in the idea that the search is what makes us human, is what's most important, far more important than concrete answers. The end of Prometheus affirms this, when Shaw makes the choice once again to go in search of knowledge, despite everything she's seen and been through. The point is that Shaw doesn't give up, kill herself or allow herself to be killed, or flee home in defeat. She keeps looking and ultimately it doesn't matter whether or not she finds that final answer (hint: it's 42). Though Prometheus leaves open the possibility of a sequel, I don't think it's necessarily inevitable. I think Scott is a good enough filmmaker to understand his own themes and aims, one of which is--you know--never quite answering the question.
There's a lot to this movie, some of which I will ramble about in other entries. It's possible to see it as a metaphysical, sideways-religious allegory, or as a more prosaic battle for life between opposing species. Any way you look at it, it's interesting and worth the time.