The Andromeda Strain,Silent Running,The Thing(great music as always with John Carpenter),Westworld,Tron,The Ice Pirates(for comic SF),The Hidden,Predator(1&2),Event Horizon.
All good ones,as indeed are the Alien-series and the Star Trek movies of course.
Blade Runner is up there,but i also probably would not pick it as the
best of all time.
Then again,i'm not sure i can
give a best...
As with other things,it varies according to mood,recently having seen,etc.,etc..
'It's just like crop circles. No matter how many aliens own up to making them, there are always a few diehards who believe that humans go out with garden rollers in the middle of the night-'