The one that started it all
I always need to remind myself that this came out in the 70's (1979) it feels more like it came out sometime in the 80's. Irregardless of when it came out it launched a whole number of sequels, most of which had Sigourney in them which is good. She does play the role of Ellen Ripley quite well, and after the first sequel I think it would have been a disappointment not to see her in the others.
This space movies starts with the space ship Nostromo receiving what is believed to be a distress call, so off they go to investigate. They land on a planet and start searching, the search party soon finds a derelict ship. This of course they must enter, not sure about that myself.
Ripley who is not part of the search crew and on their ship has actually managed to translate part of the message. It isn't a call for help after all, but more of a warning to stay away. The search party in the mean time find a chamber that contains a lot of eggs, big eggs.
One of the eggs starts to hatch, only thing is that the creature inside isn't cute and fluffy. It launches itself onto the face shield of one of the crew and actually manages to break through and wrap itself around his throat. Ripley refuses to let the search crew back on board their ship as they have an unknown organism with them, smart lady.
The search crew however manage to get on board their ship anyway, the create does detach itself from the face and neck of the particular crew member. He seems fine with only a few minor injuries. The crew have now left the planet and are eating a meal together when the "infected" crew member suddenly starts to experience chest pain. The next scene is one of the scenes that made this movie a hit, so if you haven't seen it I won't spoil it.
Now they have an alien creature on board and on the loose, and it is somewhat intelligent. Plus it has blood that would make most highly corrosive acids look weak. Who gets the feeling a lot of the crew aren't going to make it? The long and the short of it is that most of the crew don't make it.
I strongly suggest that if you haven't seen this movie you should, Ridley Scott directs this very well and builds the suspense. The action scenes are very good for something that was made in the 70's.