Terminator 2: Judgment Day

No, and this is the one to watch if you only ever watch one. It is also the film that makes every sequel structurally awkward, which is worth understanding before you decide how far down this list to go.

The inversion is the famous part: the same actor, the same model of machine, now sent back to protect the boy it was built to kill. Cameron sets it up so that you spend the first half hour certain Schwarzenegger is hunting them, then flips it in the corridor of a shopping mall. The T-1000 that replaces him as the threat is faster, quieter and played by Robert Patrick as a man who never hurries, and the liquid-metal effects were a genuine break in what films could do rather than an incremental one.

Underneath it the film is arguing with its predecessor. The first film is a closed loop in which nothing can be changed. This one insists there is no fate but what we make, and then proves it: Sarah and John destroy Cyberdyne, the arm and the chip go into the steel, Dyson dies, and the machine lowers itself into the melt so that nothing of it survives. Judgment Day is prevented. The story is finished.

That is the problem every later film inherits. A sequel has to argue either that the prevention failed or that it never happened, and the four that followed picked different answers, which is why none of them agree with each other. Watch the Special Edition if you can; it restores the Dyson material and a scene of the T-800 being taught to smile, and both deepen it.