One of my favourites (which was recently on the box) was the original B+W version of "The Day the Earth Stood Still". Excellent stuff - and there was absolutely no need to remake it.
(Alien is still better than Aliens - different styles,etc and Aliens would have to be the Special Edition)
But then, I have a soft spot for the original "Thing From Another World" which was the godfather of most modern sci-fi horrors)
Still trying to decide on a fave ..
Veni, Vidi, Aesculi
(I came, I saw, I conkered)