1. Aliens: The peak of the series and the point it will never be able to reach again unless Cameron comes back, it was a huge risk to turn a horror film into action, but in this case, it did wonders.
2. Alien: Can be a little too slow for many, but it's still a brilliant film.
3. Alien 3: The first time i watched it, i hated how the surviving characters from the previous film were offed like that, as it is, it's still really good, this was a very depressing way to close Ripley's saga, but it still did make sence.
4. Prometheus: Could have been better, sure, still not a bad movie, and if there's a film that needs an expanded version, it's this one since so many of the plot holes or problems are explained in the deleted scenes. They should have also went with the original idea of the mutation making people look more like Xenomorphs than zombies. I think comicbookgirl gives a great insight on that, i recomment anyone to watch her video.
This is the line that separates the decent Alien films from the bad, from here on are the ones i'm honestly very disapointed and that i don't think are worthy of being part of the film series.
5. Alien Ressurrection: I think that every single aspect is off in this movie, the mood, the characters, the dialogue, the tone, etc. I don't just blame the Director, i actualy blame the script more, Joss Whedon likes to put faults in everything but his scripts by saying the Direction was wrong, but from his work i don't think it would have been any less hollow if it was done the way he wanted it to be.
6. Alien vs Predator: The comics and games have shown that the idea actually has potential, the film gave the oposite impression.
7. Aliens vs Predator: Requiem - There is nothing good in this movie, you can't even see a thing of what's going on.