Prometheus had a lot of expectations behind it. Not only was it Ridley Scott returning to science fiction, but it was also being promoted as possibly a prequel to Scott's own classic, Alien. Scott himself has said that Prometheus isn't as much of a prequel to Alien as it is a film that's set in the same universe, and there in lies the problem with the film.
To put it bluntly, Prometheus should have been a prequel to Alien or it should have been it's own stand alone film, but it tried to be both and that works to the film's detriment. As a prequel to a popular but disgraced franchise, it fails miserably, but it also doesn't work as a stand alone picture because of all the blatant Alien references throughout. We get the Space Jockeys (now called Engineers), Weyland Corporation, the ship from the first Alien film, androids, Alien egg-like vases, and the ending of the film itself. Hell, just watch the trailer and you'll see tons of familiar Alien imagery, and even the same "scream" sound effect heard in the trailer for the original film.
But sadly, like most prequels, this falls prey to continuity issues and one of the big problems I had with the Star Wars prequels, where the technology seen in this is far more advanced than the technology seen in the other films. The final moments of the film are also a huge break from the continuity of the other films, and I have read Ridley Scott's explanation for this, but it still felt cheap and poorly executed. It was almost as if the writer's realized during the last thirty pages of the script that this was an Alien prequel, and they threw something together at the last minute.
This all brings me back to my original argument, that this should have just been it's own stand alone film, no ties to Alien whatsoever. Prometheus asks some pretty big questions and easily could have existed as it's own independent film. I get the feeling that they kept the ties to Alien because they knew that they would get a built in audience with it, not to mention that Prometheus was promoted as an Alien film from the beginning of it's development. Ridley Scott and company spent most of their time promoting this film as a stand alone film, but this brings me back to my argument that it should have had no ties to other films then, because all of the Alien references in it only serve to shoot the film in the foot because it builds up fanboy expectations so much.
Does Prometheus work as a stand alone film? Almost. While the initial premise is intriguing, the film falls flat. The first two Alien films are some of the most influential films of all time and created a whole new set of movie cliches, and now things seem to have come full circle as Prometheus falls victim to that same set of cliches, like the evil corporation only out for profit, the shifty android character, and the crew of poorly developed side characters who only exists to die. In the end, most of Prometheus left me lukewarm because the film didn't really have anything original to say or do.
Plot holes are also a huge flaw of this film. Several things are introduced and then never followed up on, and I left the theater with more questions than I did answers. Many elements seem to be just thrown in and then forgot about, especially one action scene that could have been completely cut and no one would have noticed.
The best thing about Prometheus is the acting. Michael Fassbender steals the show as David, the android member of the crew, making David both innocent and mysterious. David is also one of the main flaws of the film, as I was never sure about his motivations, particularly one seemingly villainous action of his. Charlize Theron and Idris Elba are also fantastic in what were essentially both two dimensional characters (the scene where Elba flirts with Theron was probably my favorite scene in the film). Guy Pierce makes a surprise appearance, and does just fine, though he seems miscast.
Overall, Prometheus seemed like it couldn't decide if it wanted to be a stand alone film or an Alien prequel, and it worked against the film. Great acting made me stay with the film, but a cliched story and flat characters kept this from being something truly special. I would say that Prometheus was the first big disappointment of the summer.