Prequel or Standalone movie its up to you to decide, without any spoilers.
Alien was and still is one of my favourite movies of all time, it was scary and not just because of the title monster. It had many deep layers embedded underneath its well written and fleshed out story. That was also the last time Ridley Scott touched this series. Now I'm not really going to go in depth with the other films as they branched off into other paths and in my opinion lost what made Alien so great. Aliens was a good movie, lots of explosions and hopelessness but it just wasn't the same. Prometheus in my opinion is essentially a prequel to Alien, and not that its a bad thing. This movie does so much right, though it tends to follow in the originals footsteps a little to closely. What made the original so good is still evident in this piece and for the most part it is a truly entertaining movie. Though at times the pacing feels a little to fast and the dialogue is less then stellar in a few encounters this movie still manages to be one of the best thats come out in the past few months. The only real stand out in my opinion is scenes involving David the cyborg crew member. In this character you get a sense that his personality is a mix of Ash's from the original and Bishop from the sequel. He is the high point of the film. Its not that the other characters had been terrible but they felt stale in a way, almost as if you've seen their respective archetypes before.
The cinematography and visuals are drop dead gorgeous, say what you want about Ridley Scotts abilities as a director he knows how to make beautiful and breathtaking scenes. From the Prometheus herself to the Alien environment this is by far one of the best looking movies out on the market. The audio and sound design was also top notch, you'll find your standard sci-fi fare here. It greats a good amount of tense moments and the nuances are great. When Ridley Scott directs a good movie it shows, from the characters to the flow and visuals of the movie Scott can create a piece that truly can stand the test of time.
+Sound design is top notch
+Michael Fassbender is fantastic
-almost too much like Alien
-Feels like it could have been longer
I've heard Scott say consistently that this is a standalone movie apart from the Alien ones, but it just uses the same universe. After watching this movie and I'm sure you will see it too this is 100% most likely a prequel. It's not a bad then, maybe he will make another Alien movie or a sequel to the prequel which hopefully doesn't spawn another series of lacklustre sequels?!?!?!!!? Whatever anything's better then the AVP movies.