Add any movies you consider heavily underrated, also.
Most Helpful Guy
I'm not sure if these count as older or if you want to go all the way to B&W, but some 80s films:
Total Recall (1990)
The Running Man
What About Bob?
Full Eclipse (1993)
These are a few. One that I consider really overlooked that's newer is Gattaca (1997) as kind of a poetic sci-fi.