One of my favorites, and one of the few really good ones of the genre from the 1950's.
I loved
Forbidden Planet. It's one of those movies I get more out of every time I see it. I always thought
Star Trek owed a debt of gratitude to FP, especially in the relationship between the captain and the ship's doctor. In the so-bad-it's-
awesome episode of TOS, "Spock's Brain" Dr. McCoy even uses a Krell-like intellect expander in an underground complex - right out of FP.
There were a lot of quickly made Sci-Fi cheapies made in the 50s, but also some very interesting films:
The Day the Earth Stood Still (the original),
The Thing From Another World (I also really liked the 80s version with Kurt Russell; much more like the original short story, "Who Goes There"),
Invasion of the Body Snatchers, Invaders From Mars -- all of those hold up very well, I think. I also have a soft spot for the 1953 version of
War of the Worlds, although I must qualify that with the caveat that the film gutted H.G. Wells' book of almost all its philosophical content. When I was a little boy I remember being very impressed by the Martian landers, which were also a departure from Wells' mechanical tripods.
I could go on and on, but I'll shut up...for now.
JAMES