The first two entries in the Alien franchise are almost universally considered the best, and each is a beloved classic in its own right, but which do you think is the better film, and why?

Good question.  The first Alien is pure Sci Fi horror while the sequel, Aliens is Sci Fi Horror Action.  The sequel is my choice personally.  Not because it is a better film, but because it is a better rewatch.  It is more memorable in certain ways due to it's quotability, it's characters, and the end is fantastic.  It is the perfect sequel that takes what made the first movie good and expands on it.

Difficult choice. Both are amazing. Still have to give it to the original, the atmosphere and the way the creature is shown, or not shown, as well as the layered plot (seems simple on the surface, but gets deeper once the actual motive of the company is revealed), which all makes it one of the best horror films ever made, appeal more to me than the more straightforward Sci-fi action of the sequel. But like I said, the sequel is almost equally amazing, both far above the rest of tue franchise, though I do like the third movie as well and even appreciate the fourth, Prometheus and the new one from a couple years ago. AvP is okay for what it is, but the sequel to that is dreadful.

Alien. Im more into horror than action.

Gotta go for the original. It has a better character arc for Jonesy.

Aliens is a fantastic sequel, but Alien is one near perfect film.

The original as I usually prefer the freshness of the first entries.

You can't beat the originality of the original Alien. Aliens was a good film, but you always feel that you've seen something like that elsewhere (even if that elsewhere was a later copy of Aliens).

In case people start mentioning other films that have Alien in the title, I should point out: there are two Alien movies... Just like there are three Star Wars movies...

Alien is a incredible Scifi-horror movie.
Aliens is a action blockbuster, a good fun movie, but not at the Alien level. The first movie has an incredible ambient,good acting and incredible visuals.
Aliens has very flat characters (only Bishop is interesting) and break the "Invencibility" of the Alien menace with the typical "Americans kill anything with guns"
Unpopular opinion: Alien 3 is a really good movie, people dont like it because they wanted Aliens Again and not something original. Alien 3 has a new,diferent setting and interesting characters. And the Alien is a really invencible threat again.

Sorry for my bad english.

Aliens is the rare time when a sequel beats the original for me. Alien is a fantastic horror movie and right up there with the best in horror. It does drag on a bit in scenes. Aliens is non stop action, and the only small gripe I have with it in Newt is a bit annoying. The characters in both movies are excellent and well acted, but I preferred the characters in Aliens especially Hudson, Vasquez, and Frost. if I want a great classic horror movie Alien is a great choice, if I want one of the best action movies Aliens is the choice!