For me, it's a close tie between ALIEN and ALIENS, but ALIEN wins it.
ALIEN is just so intriguing and beautiful. The Nostromo is basically a character in itself... what an awesome set. Then there's the character development, the awesome acting (they even talk over eachother like in real life), etc. You don't see many movies with such a small cast, let alone a successful one. Then there's the fact that this was the introduction of the ALIEN as a franchise. You don't know what's going to happen.... the plot just keep shifting into something else until you have this FREAK creature going around picking everyone off. It really captures the horror the crew was going through, and gives you a realistic perspective. All the little plot details really just make the film seem more real. You get little random events instead of conveniently just placing the Alien into the plot... first there's the derelict, the space jockey, then the plot swerve with Ash, etc. Even the landing on LV-426 doesn't go as planned. Today in Hollywood, you really don't get plot devices like this, and instead you just see a plot that moves too quickly into the main point and theme it's trying to make, detracting a lot of realism from its story. The concept of the derelict in ALIEN is very bizarre, the fossilization, etc. The directors could have taken the easy route and just have the Nostromo crew discover the eggs on the planet, instead we get all these other details which are a lot more like how an alien discovery could actually take place in real life. It feels like a real space expedition on a foreign planet. And much more could be added to the analysis of what a great movie ALIEN is.
ALIENS is great too, but more straight forward.
Alien3 and Resurrection aren't too good. I used to like Alien3 but I'm beginning to think it sucks. AVP I thought was "OK".... I haven't fully watched AVPR yet. I tried watching it the other day but couldn't even get through it. I could go watch it now, but instead I think I'm gonna go make some popcorn and a milkshake, and watch ALIEN.
So...
1. ALIEN
2. ALIENS
(big gap)
3. AVP
4. ALIEN3
5. ALIEN RESURRECTION
6. AVP: R
