Vote for the greatest sci-fi film ever, I try to include all

1. Them!
   
2. Planet of the Apes (with Heston)
3. The Andromeda Strain
4. The Day the Earth Stood Still (with Rennie)
5. Forbidden Planet
6. Silent Running
7. Quatermass and the Pit*
8. Lifeforce

Honorable mention to Fantastic Voyage, which I also own on DVD.

*EDIT:  I own the TV version on DVD.  But I do have a VHS copy of the movie version (AKA "Five Million Years to Earth").  If the a reasonably priced Region 1 copy of the movie was available, I'd buy it in a heartbeat.