I saw the movie in the theater when I was about 12 years old. I loved it without knowing why, but it seems obvious now, looking back more than 50 years. For one thing, it's a simple story that I'd seen plenty of times in the black-and-white B-westerns at Saturday matinees: ranchers vs. homesteaders. Shane was in beautiful color, but it was black-and-white in its depiction of two of the central characters. There's never any doubt that Shane is the good guy and that Jack Palance isn't. Palance is great as a man who's as thoroughly evil as a man can be, and loves it. He dresses entirely in black and is a real prince of darkness. The scene where he provokes Elisha Cook, Jr., into drawing on him was a shocker to me, and probably to some of the adults in the audience, too.
That's not to say the movie's morally simplistic. Shane's relationship with Marian Stewart (Jean Arthur) and the ranchers' grievances against the homesteaders are more complex that you might think at first, and they give the movie some depth.
Another typical western element is the use of the lone stranger who rides in to set things right, reluctantly, of course. Alan Ladd was never anybody's idea of a great actor, but he's really good here, mainly because he underplays everything. He's all quiet strength.
There's also the coming-of-age story with Brandon De Wilde, the kid who begins to realize that things aren't as simple as he thought and that even doing the right thing has a price.
And then there's the scenery. This must surely be one of the best-looking westerns ever filmed, in Technicolor and wide screen, with the Tetons as a backdrop to a lot of the dramatic action. To a kid who'd never been out of Central Texas, it was like seeing a movie filmed on another world.
There are people who don't Shane is a great movie, but it will always be on my list of best westerns. (The Mad parody is pretty good, too.)