5 - Aliens
It must have been tough following up from Ridley Scott's Alien. The film was genius. However, James Cameron has his own brand of genius and wisely didn't dare emulate the tense, claustrophobic atmosphere of the original. Instead he threw Ripley and a group of space marines into a colony built on the site of the nest of alien eggs. Needless to say, everyone is dead and the place is now populated by aliens. It isn't slow and terrifying like the original, it is machine gun toting, flame throwing, nuclear air striking, robotic arm boxing and terrifying.
Best bit: "Get away from her you bitch!"