First off, this is not really a sequel to Alien (1979). Alien was a horror film. It stuck a bunch of people together in a room and then had them picked off one by one until Sigourney Weaver’s Ripley rose to the occasion and stopped the killer (the alien). Aliens on the other hand is more along the lines of the old formula of sticking a bunch of good guys in a room and having the bad guys on the outside trying to get in. This is a an action/suspense film.
Second, this is essentially James Cameron’s testing ground for many of the scenes and characters that he would later use in Terminator 2: Judgment Day (1991). Ripley is Sarah Connor, no doubt about it. The opening sequences with her in the hospital are almost shot for shot the same as when Sarah Connor is in the hospital telling them that there really are Terminators despite the lack of physical evidence. Michael Biehn is playing the same character from the original Terminator, a protector for Sarah Connor. The little girl Newt is John Connor, the child to be protected. Lance Henrikson’s synthetic lifeform is Arnold who is there to help and protect. Ripley is distrustful of Henrikson because of her previous experience with a synthetic, but comes to appreciate Henrikson when he risks his life to save her. Just like Sarah being distrustful of Arnold because of the events of the first film. The list goes on and on. On a side note, you can also see Bill Paxton’s pants wetting car salesmen from True Lies (1994) here as a marine who would wet his pants if he wasn’t holding an enormous gun in his hand.
Finally, it doesn’t matter that it is a prototype for T2. The film is a fantastic piece of action/suspense complete with James Cameron’s signature of technology gone wrong. It isn’t better than the original, but definitely as good.