It sounds like I'm in the minority here, but I think Alien is better than Aliens. Alien was fantastic, it was the unknown, it was atmospheric, and the atmosphere was genuinely tense, it lends itself fully to the horror genre as opposed to the action genre, which for this film was a definite plus. The crew are not set up to fight and have to battle on with what they can find, and the never knowing when or where the Alien will strike, alá John hurt at breakfast - what an amazing scene that was first time round.
Aliens for me, is loads of fun, but it's a dumbed down 80's version of a true classic. It's a case of we've had a mega succesful movie, let's throw in some strereotypical characters, (the black shouty boss, Apone, found in every movie Police Station or army platoon, the wacky one liner in Hudson, the beast of woman Vasquez who loves her guns, and the cool calm resourceful lead in Michael Biehn who basically took his Kyle Reese charactor from two years previous and reprised him with futuristic weapons in Aliens, not to mention the manipulative corporate creep who appears so nice to start with Gorman I think), then lets throw in loads of guns, and multiply the numbers of bad guys a thousand fold, and seeing as it's the 80's movie, lets have a big boss monster at the end....
But it is a classic, it is loads of fun, and I love it, own it and watch it every time it's on. But it's just not a patch on the original in my opinion. Mostly due to it's formula, it just got run through the 80's action movie wizard. Alien was orignal.
Incidentally, I also rate Alien3 as much as I do Aliens. And I suspect I'm in an even smaller minority here and will be subject to much disgust and derision for this opinion. This again is down to the story line though, it's far more involved, David Fincher has gone to great length to recreate the atmosphere and tensity(is this a word) of the original, again it's against all odds, the inmates using resourcefulness to combat the Alien as opposed to the aim and shoot your big powerful gun. The only thing that lets it down is the CGI on the Alien itself in the long shots.
Alien: Resurrection however, can suck my balls.