I'd put Aliens and Alien (in that order) at the top! Great sets, great suspense great action, and some engrossing acting.

2001 was a bit squeeky clean - sterile in fact. No arguments. No blood sweat and tears. Well spaced sentences and no background noise. Lots of white in the sets...Maybe that was the 1960s view of the 21st century? I also think that if a film has something to say it should spit it out. 'Contact' did they very well.

"Time is what prevents everything from happening at once" - John Wheeler