Star Trek: The Wrath of Khan is quite good. It's pretty clever and well-written. And unlike many of the Star Trek films that have come since, it has some memorable characters (even the villain!). William Shatner and Leonard Nimoy make a great pair onscreen.
Dark City is highly reminiscent of The Matrix (which it preceded, by a year). The story is fairly intriguing but the acting is so-so. The two things really worth seeing are the cool (and dark) visual style and Kiefer Sutherland playing a mad scientist type.