Stalker,
Undefined,
17 years ago
Aliens is without doubt the best in the series in my opinion. The tense set up, the cast, the creatures...all completely unmatched by any of the other Alien films.
Alien3 would be second on my list. The dark, gothic horror style really gave it a very unique & individual tone to the rest of the movies, the Special Edition in particular is one of the best in the series.
Treading roughly the same ground as the third film is the original Ridley Scott classic. While it stands head & shoulders above many similar films, it still doesn't quite match the excellence of its sequel, although in its own right, it's still an iconic Sci-Fi/horror classic.
Far beneath all these films however is Alien Resurrection, a movie which succeeded in creating a suitably dark & grotesque feel to the setting & creatures, but also tampered with the franchise to the point of violation. DNA mixing, cloning, & horrible abominations were the downfall of the movie in my opinion, & were not helped in any way by the mediocre-to-terrible cast, & some occasionally cheesy moments. I'm sure many fans would like nothing more than to simply erase it from their minds & pretend that it never existed.