Raiders of the Lost Ark

Raiders of the Lost Ark ★★★★★

It really isn't just nostalgia.
I saw this in the theater when I was ten. I didn't know anything about genres then, but if I had, I would enthusiastically have said that this set the standard for action/adventure films. Watching it now, more than thirty years later, it is still the standard. It has simply never been equaled. There's not a casting choice, not a plot development, not a line of dialog, not a single frame I would change about this.
If you're part of the tiny fraction of one percent of the population who has never seen it, then SEE IT. I would recommend this movie to literally anyone, without any reservations of any kind. Just see it.
Dodge the sequels, though.