Let's get straight to the point!

A L I E N

Singular

( A   L   I   E   N )

slightly edges out to Aliens if I have to pick.

Straight up Alien. No hesitation. No survivors.

Alien....Then again, Aliens..

Hell, I don't really know...

I think the Question should be which do you prefer...

Or if you could only ever Watch One Alien movie again out of those TWO which would it be..

For me... a combination of the TWO would been great lol

If i had to choose one... then it would have to be ALIEN however Aliens comes close, but its more a Popcorn flick and the more Older i get, Aliens just seems to lose its Magic...

Its a very 15-25 year olds kind of Movie IMO, but a Good Action/Popcorn Flick at that.

Alien 

A L I E N

No doubt, no hesitation.

ALIEN (same as 1hr ago)

I watched Alien first, very good, then when Aliens landed i totally loved it. 

However, same as BigDave, as the years go i guess your tastes change and im back to Alien. 

I think that the question is put in a strange way. It would have been better if it would simply have been do you prefer alien or aliens. The answer is: it depends what I feel like watching for the moment. When I feel like watching a horror movie I watch Alien and when I want an action movie I watch Aliens since they to me belong in different genres. Aliens was my favorite when I was younger but now I prefer Alien but I am not sure why. Both Alien and Alien 3 are better than Aliens IMO.

.............................Gangbusters.

ALIEN

Can you have ALIEN, and still have satisfying Action?

Yes.

It's tricky, but it's do-able, the KEY thing is like business:

Location-Location-Location.