Aliens - The original Alien is hailed as one of the best films of its genre. It was shocking, subversive and wickedly haunting. Few people could topple the challenge of making a film that could equal that first one, but James Cameron brought some new elements to the table which led to a film that is often spoken in the same breath as Godfather Part 2 and The Empire Strikes Back. Aliens works as a sequel by further developing the survivor of the first film, as well as furthering the mythology of the alien itself. If that had been all, it still would stand as a good movie but just merely be a sequel to Alien. No. What Aliens does is infuse other layers that set it apart as its own film, while continuing the narrative set up in the first movie.
Aliens is also a film about mothers (which was the film's scripted title at one point). Much of the film can be viewed as an allegory for motherhood and ends with a conflict between two mothers. The film is also a metaphor to the Vietnam war. It is interesting to pair this film with Rambo: First Blood Part 2 because the two films (both scripted by Cameron, and written simultaneously) are both expressing long held responses to the conflict in Vietnam. Where Rambo is very much a revisionist's fantasy, Aliens is a rather transparent retelling of the war from the American perspective. One unfortunate thing that happens when you take a race of people and reduce them to being viscous animals through the allegory is that the film's politics get a little cringey. That said, Aliens is a masterpiece of Action, Sci-Fi and Sequel cinema that earned Sigourney Weaver an Oscar nomination for Best Actress. There are two cuts of this film. See the director's cut, which is infinitely better at setting up character motivation and building the tension.