One of the very few horror movies I own, Aliens was one of the few sequels that actually improved on the original movie. Its interesting to note that the director's cut, which often is worse than the original, to my mind is essential viewing. It adds a scene giving us a glimpse of the colonists just before they discover the aliens, explains why Ripley is so obsessed with Newt, and the sentry guns show the marines do have some other tricks up their sleeves.
The characters in this film really do stand out, from the backstabbing company man Burke, to the marines Hudson and Vasquez, and of course Riply herself.
Although fairly old now, it still stands the test of time fairly well in most scenes, although as with so many older Sci-Fi films you have to turn a blind eye to the dated monitor screens and graphics.
Overall a great movie, marking the high point in a franchise that crashed after this movie.