The good news: movies based on comic books keep getting better and better. I loved “The Avengers” and the audience I saw it with clearly loved it as well.
The bad news: sci-fi movies are getting dumber. Well-read audiences are not, apparently, inspiring well-written scripts.
I've already expressed my lack of respect for the “Avatar” script. So when I say that “Prometheus” is better, but only barely, that should be understood as damning with faint praise.
Visually, it's gorgeous, and, like “Avatar” is probably worth seeing in 3D if that's not too expensive in your neck of the woods. But understand, going in, that you're about to watch a film which includes scintillating (and revealing) dialogue like, “This is a scientific expedition; no guns.” This is a movie where someone dies because they apparently forget they can turn left or right. This is a movie where a guy with a PhD in biology, in a dangerous environment, decides to pet an alien creature he can't see most of. Where the guy who's directing the hovering drones mapping out the alien complex gets lost. Where emotionless androids enjoy classic cinema.
As others have noted, the entire third act hinges on everyone acting in the best interests of the plot-beats instead of like self-interested (or even compassionate) human beings. I'm leery about declaring the movie has an overt Pro Life chip on its shoulder only because I have a hard time believing Hollywood would purposefully make a Pro Life movie. And yet, the only way to make sense of the last act is to say all things moved in service to heavy-handed allegory.
That said, some of the acting is excellent, the scenery and props look great, and the body-horror is pleasantly spine-shivering. I can see myself watching this one again, but I'd only own it if the remaining films in the series (the ending invites, nay, demands at least one sequel) are compelling.
PS - Yes, I know, actors hate to work in helmets and masks, but seriously? My respect for Hugo Weaving continues to skyrocket.