I made a quick list of some of my favorites in no particular order. Whenever I try to think up a list-I always forget some great ones. (More lists to come)

It: The Terror from Beyond Space- 1958-influenced the Alien series
Alien 1 &2
Terminator 1 & 2
Forbbiden Planet-1956
The Blob-1958

The Thing- 1951 ( Carpenter in '82 was good also)
The Day the Earth Stood Still-1951
Invasion of the Body Snatchers-1956
The Matrix-1999
Blade Runner-1982
The Empire Strikes Back-1980

Them-1954 2001-A Space Odyssey-1968 Predator-1987

(Update): I think I'll post a C&L TOP 50 list or something like that after the holidays with your help, so please join in.