Raiders of the Lost Ark

No, and ignore the chronological toggle on this one. Temple of Doom sorts first because it is set a year earlier, and starting there would be a mistake: these films share no continuity worth protecting, so the only question is which is the better introduction, and it is not close.

What makes it work is the competence. Indy is never ahead of the situation. He loses the idol in the first ten minutes, loses the Ark twice, gets beaten up continuously, and spends the climax tied to a post with his eyes shut. The film is a chain of improvisations by a man who is good at his job and permanently out of his depth, and Ford plays exhaustion better than anyone has before or since. Marion is written as an equal who is furious with him on arrival and stays furious, which is why she is the only love interest in the series anyone remembers.

There is a well-known structural objection: Indy changes nothing. If he had stayed home the Nazis would have opened the Ark and died anyway. It is true, and it does not matter, because the film is not about consequence. It is about whether this specific man can stay alive from one scene to the next, and the plot is a delivery system for that question.

Almost everything in it is real. The truck chase was shot with a stunt performer dragged under a moving vehicle, the boulder is a physical object, and the few optical effects at the end are deployed once, at the climax, on something explicitly supernatural. Forty-five years on it is still the benchmark.