"Blade Runner" was another great one. I've seen it so many times I think I would be bored by it now ...with or without director's cut.
In it's day Alien was the best. Huge theatre...big crowd.... great buzz about it and was the 2nd day it was out. I had to look away from the movie screen at times..... I was scared which rarely happens
Go buy the book Future Noir: The Making of Blade Runner by Paul M. Sammon.
If you think that movie was interesting, the story behind it is even more interesting. Also, get a hold of the Blade Runner PC Game (Yes it works under Windows 2000 Pro Service Pack 2). Both of these things are a bit dated, but worth the money.