One film that's always left off these lists and certainly deserves a high place is 1944's lavish and magnificent The Uninvited. It's lush with an intricate plot, frights, scares and chills that hold out to this day, and a twist ending.
Also, 1947's The Ghost and Mrs. Muir since comedic ghost flicks make the list. It's one of those movies you can't stop watching, but make sure to have plenty of kleenex for the finale.
Gerard