Alien (2003 Director's Cut):
I got the Alien Anthology for Christmas or my birthday a couple of years ago and for one reason or another I haven't had a chance to watch it since then.  Well, I finally managed to watch it.
The movie came out in 1979, the directors cut came out in 2003 and it is now 2014. This version starts with Ridley Scott, talking for just a second saying he is proud of the film and that he had added some new footage that had never been seen before and changed a few things that needed fixing.
I never saw the original Alien in the theater, which really isn't surprising as I was nine at the time. In fact I didn't see Alien until after I had seen Aliens.  Since then, I would guess that I have seen the original movie maybe three times (not counting today's viewing). I've not seen the film enough times to be considered an expert on it, but I didn't see anything that stuck out as new or substantially different.
The Alien movies are supposedly 'sci-fi' movies, but let's be realistic. The four movies are not all of the same genre. The later three are more of what you would consider a sci-fi action movie. The first one is a straight up horror movie. Sure it's set in space and in the future, but don't kid yourself.
The movie holds up pretty good even though it is now thirty-five years old. The special effects are pretty dated in some places.  The computer systems on the ship are laughably low-tech, but I suppose in 1979 they were cutting edge. The shots of the ship flying in space are pretty bad, but the real loser of the spfx is when they reactivate Ash's head so that they can talk to him. The detached head they manipulate and the talking head  are not even close to similar. Actually, I can remember thinking the same thing the first time I saw the movie in the late 80's.
The super secret computer interface room that only the captain is allowed to go into is kind of dorky too. It's got eight million blinking lights on the walls that would serve zero purpose. I wish they had just made that room dark and spooky like the rest of the movie. 
Anyway, as for the rest of the movie, as previously stated, it's scary. Really scary. Super duper scary. 
They do a great job of never really letting you see the alien monster clearly. It's always around a corner, or there's bad lighting or there's steam everywhere. Occasionally you get a clear look at an arm and and it's obvious that it's a man in a suit, but those fleeting moments don't make you feel much better.
As I said, I've seen it enough times to know what happens and it's still a nail biter.
Other things that stand out for me are:
- Awesome cast including: Sigourney Weaver and Yaphet Kotto. 
- I like that they bothered to make the alien ship in Prometheus very similar if not identical to the one from this movie. 
- I've also always liked how the Alien monster was super drooly. 
Finally, let me just say that if I was on a space ship and there was a monster running around killing everyone, the cat better get its own butt into the escape pod, because I will straight up leave its butt behind.
Now excuse me while I go watch something nice and safe. Maybe a musical or a kid's movie.
Alien (2003 Director's Cut): A
 - Mainly it's because, if the Bear and the Bean are around there's no chance I'm watching it and the Pook isn't a fan either.
 - Which I did see in the theater, but we'll save that for another day.
 - Pretty dated is a nice way of saying really old looking.
 - Which is just the actor sticking his head through a board.
 - There are some other spfx moments that fall short (like the stiff unbending baby alien), but really they are not that bad and again, this was 1979.
 - Especially when you are watching it alone because everyone else in the house is in Tennessee.
 - He's awesome. Homocide: Life on the Streets anyone?
 - Prometheus still sucks in the plot department, but it's a nice bit of continuity.
 - Don't ask me why.