Overall an ok movie...not the best but just ok. Visually, it is phenomenal, but that's about it. Here are the problems I see with this movie:
1) It's a rehash of Alien, no more and no less. It doesn't break new ground; it doesn't have any surprises. If you were to describe both movies in two sentences you would get the same thing. In fact, if you've seen Alien, you can predict a certain scene towards the end of Prometheus.
2) The excuse to get the crew onto the planet is pretty lame. I admit I used to like the "ancient astronaut" theory (look it up or see the movie, i don't want to spoil it for you). But cmon...it has been used many times before including AVP 1.
3) The origin of the xenomorph and the Space Jockeys. I know some people will disagree with me on this but I think these characters were better left as they were...without any explanation as to who they are. It kinda ruined the magic for me when we find out what the SJ's really look like.
4) A particular scene in the movie involving ....a medical operation shall we say. Won't go into details but it kinda took me out of the movie when this person gets the procedure done and then he/she is running around like nothing happened a few minutes after....