People are still posting here? Wow.
My thoughts:
The film is full of ideas, largely circling around creation and religion. But none of them are new, and none of them are explored in very interesting ways. Every concept explored in Prometheus has been done elsewhere to greater effect. Probably in an episode of Star Trek somewhere.
The film looks spectacular, as film fans have come to expect from Ridley Scott projects but they're merely a nicely patterned shell around a seriously hollow story. On the face of things, explorers following an ancient roadmap to the stars to meet what could be our creators seems like a fascinating starting point. Unfortunately the film only presents us with questions upon questions and little reason to care about the answers.
An audience's ability to get invested in a story hinges largely on the characters and that's one area where Prometheus really suffers for me, because there aren't any characters. At least none that had a strong enough identity to care about them dying horribly. There's a cast of brilliant actors in the film that just didn't have very good material to work with. Characters do and say things that come out of nowhere or seem contrary to what we'd expect of them and there is little time devoted to making us understand why anyone does anything.
The film could have gone in a Lovecraft-esque cosmic horror direction very easily given the concept. Yet somehow its horror elements always feel at odds with the ideas Ridley Scott obviously wants to explore re: the engineers creating humans and humans creating androids. The film struggles to find a tone and stick with it while it's caught up in its attempts to be both profound and frightening at the same time.
Notice I didn't mention Alien or the film's connection to Alien at all. That's because the film scarcely has a connection, beyond some superficial elements like the Engineers' aesthetic and the Weyland corporation. It feels like a totally separate movie and I'm curious whether it would have been better if it had never tried to link itself to Alien in the first place.
All in all, Prometheus is a well-crafted film in most respects, but its foundation is a script that could have done with some heavy rewrites to really make it good. It's never offensive, but it's frequently disappointing and baffling enough to get a 3/5 from me.