Agree on The Day the Earth Stood Still, Forbidden Planet, and BladeRunner
Invasion of the Body Snatchers (both versions)
Day of the Triffids (OK)
2001
THX1138
The big problem is that some of the best sci-fi authors have just not translated to film well, only Bradbury's Fahrenheit 451 works most other adaptations of his stories only work as TV episodes (IMHO).
If you want to have fun there are dozens of Japanese films with strange social commentary such as Godzilla vs the Smog Monster and all the Roger Corman films. I've spent 60yr. watching them all.