I'd say either Rambo 2 or sleep because the rest of those movies either have a lot of depth to them, are about 3 hours long, or both.
For Godfather, it's a pretty shallow story so you could probably follow everything along half-asleep. I didn't like the writing at all though but everything else had very high quality.
For the other three, Casablanca is the most important out of all those movies. Patton was a good movie too, but they did censor how much he swore. I never saw KOH but everybody says that the director's cut was a lot better.