How could you forget The Day the Earth Stood Still?
Yeah, that's another good one. You also have to include Earth vs the Flying Saucers and The Thing that Challenged the World.
Even the schlocky stuff from the 50's was good, such as The Blob, Invaders from Mars, and Monsters from Space.
I have a good print of The Day the Earth Stood Still on DVD. Great production values, but an unbearably preachy script that looks worse every time I see it.
The basic premis is that the earth people have made a mess of things by trying to make everybody do what they're told, so the federation of good guys will blow us up if we don't do what we're told. War is evil unless its run by the good guys.