Terminator - Guy goes back in time to impregnate a woman so that the savior of the future can be born while protecting her from a machine sent back to kill her.
Terminator 2 - The woman who gave birth of the future tries to keep him alive with the help of a similar model of the machine to protect it from another.
The only thing in common is the protection thing.
Alien - Typical slasher movie, except with an alien instead of a knife wielding psychopath in a mask, and in a space ship instead of an Earth-based location.
Aliens- A retelling of the Vietnam War, featuring the survivor of the first film, showing a technically advanced group of marines getting their asses handed to them from a non-technically advanced group of aliens. (Does that remind you of any other James Cameron movie?)
First 15 minutes or so is a remake, due to the fact that the original cabin burnt down AND New Line Cinema held the rights to the first film, thus not allowing Raimi the ability to reuse the footage from the first film to recap the events. After the moment Ash gets attacked, it's a continuation of the story with new material.
Shark shows up, eats people, Brody suspects shark and tries to close the beaches, Mayor tries to deny it. Second half of the film is set out at sea, Brody kills the shark in the end.
Actually, that shouldn't be on here, should it? I say that because it's only the first fifteen minutes that's a remake (which was intentional due to the fact that they couldn't get the rights to reuse the original footage from the first film, hence the reason why at the start of the film, it shows just Ash and Linda heading to the cabin).