I Married a Monster from Outer Space. That one is lots of fun.
I'm glad you mentioned that one-I was just about too! Virtual karma!
One that is sadly overlooked is THE MAN FROM PLANET X (1951).
It was directed by old horror and noir director Edgar J. Ulmer-the man behind the Lugosi/Karloff classic the BLACK CAT (1934) and the classic noir D.O.A. (1950).
Much like the old monster movies-it's very atmospheric.
And the alien is NOT the bad guy...he's captured and tortured by a scientist.
Though I must say-the alien's face looks like a cardboard mask....which in it's own way is kinda creepy...