Absolutely LOVED "The Day The Earth Stood Still" as a kid. Introduced it to my daughter when she was a child via the magic of VHS. She to, loved it and we would watch it every now and then.
Gotta' find a DVD of it "one of these days" along with some of my other old favorites.
Yes, the Forbidden Planet was a dandy, as was "Earth vs Flying Saucers".
As a kid, I also enjoyed the EARLY Japanese monster movies:
"Godzilla" (the original and not the goofy sequels), and "Rodan".
Then there were the "WTF?" movies with really poor plots, poor acting, and even worse special effects: Anyone remember the old sci-fi named "The Claw"? The evil vermin was a huge bird that sort of looked like a retarded buzzard! Truly awful on all counts... BUT... I enjoyed it as a kid!
Ah the memories!