Blade Runner and Alien. Ridley Scott is responsible for both of them, two of the most renowned sci-fi movies of all time. After 30 years, the Gladiator director returns to the genre with Prometheus, a quasi-prequel to Alien that seeks to explain the origins of mankind, and at least hint at how those acid-spewing, face-hugging teddy bears came to be. A beautiful and suspenseful action-thriller, Prometheus isn't perfect, but it still stands among the best of the genre.

Expectations. They can be a bitch. As I told many people in the weeks leading up to the film's release, there were only two movies this summer that, if either were to disappoint, would make me angry. One is The Dark Knight Rises, and the other was Prometheus. I can usually keep expectations in check, but with these two, I am and was expecting excellence.

Prometheus is a very, very good movie. "Excellence" may come in time, after a few more viewings.

The movie that is now Prometheus began as a direct prequel to Alien, but was rewritten to be something much different so as not to just repeat what's already been done before. The result is a film that is not about those acid-spewing creatures, but a story of more grandiose fashion that is set in the same world and timeline.

In Prometheus, we are introduced to Dr. Elizabeth Shaw (Noomi Rapace), an anthropologist who discovers a message in ancient cave drawings on Earth that she believes is an invitation by the "Engineers" of humanity. Several years later, she, along with a crew of scientists, security personnel and the corporate investors who are funding her expedition, arrive at a distant planet in search of answers. The answers she seeks aren't as friendly as she was expecting.

With superb special effects and Ridley Scott's fine touch, Prometheus is a captivating film that builds slowly but steadily to a boiling point - and then proceeds in an all-hell-has-broken-loose fashion. Scott's attention to detail, and ability to build suspense and maintain it, is on full display. He's never too hasty in his approach as he lets the story and characters develop at their own pace, which in turn allows anticipation to compound throughout the first act.

When the first alien does make an appearance - not a face hugger, but something close enough - Prometheus suddenly ratchets up to another level and things get really fun.

The best and worst part about Prometheus is that you don't know what to expect. The mystery - of the Engineers, of the Aliens, of the direction the film will go - is intriguing and drives the film. And yet when the creatures that bear some similarity to those found in Alien emerge, I wanted more of that. There was a part of me that wanted something epic, something groundbreaking and new, and yet the other part wanted shit to just hit the fan and for Scott to unleash his acid-spewing beasts upon the unsuspecting crew.

Prometheus falls somewhere in the middle, never completely attaining the epic nature Scott was striving for but also denying me a full rampage of Aliens that I so desperately wanted (and no, the Alien vs. Predator movies don't help in this regard). Again, the movie is very, very good, but it will take me a while to fully appreciate what Scott has created.

Even still, there are some things that didn't entirely work. There are some minor issues that gnawed at me (why the scientists would take their helmets off when investigating biological matter, or why a guy who just a minute before had been frightened to death of the idea of aliens would approach a living, breathing one that looks like a snake and try to poke it in the head, etc.), but the third act, at times, felt too conventional. (SPOILER ALERT) The captain's instant decision to sacrifice himself seemed abrupt; his character hadn't been developed enough for this suddenly courageous act to be believable. Also, after building up Charlize Theron's character in unique fashion, Scott doesn't do a lot with her.

(MORE SPOILERS) Prometheus also raises more questions than it answered: why does the alien DNA mutate one guy into a raging psychopath, rather than use his body as a host to give birth to a new creature? What is the Engineer's motive for killing everyone? Why are the other aliens on the ship to begin with? Scott alludes to answers but never really gives them.

Nevertheless, these complaints are minor in the scheme of things.

On the positive side, the acting is consistently excellent. Noomi Rapace is no Signourey Weaver, but she turns in a strong performance nonetheless. Charlize Theron, who last week stole the show in Snow White and the Huntsman, is great as well. And Michael Fassbender is simply superb. An android, his character is at once innocently curious and maliciously evil thanks to his inability to feel or be afraid of consequences to his actions. Like Ian Holm and Lance Henriksen before him, Fassbender defies the confines of "being a robot" and delivers a stellar performance.

While I would have liked to see more of the traditional Aliens and a few other tweaks, Prometheus is one of the best mainstream sci-fi thrillers to come along in a long time. Does Prometheus rank among Alien and Blade Runner? It's too early to tell, but it's worth the discussion. That alone says it all.

Review by Erik Samdahl unless otherwise indicated.