A few thoughts: While I know a lot of people throw out hyperbole like it's going out of style (please let it go out of style...), I feel it's worth noting that this is quite possibly the greatest science fiction film ever made. From the intricate sets, badass robot design, ahead-of-its-time special effects, great character development, and sheer inventiveness in its scope and ideas, there is so much to love about this movie it's hard to compress it to under 200 words. One of the first movies to be set almost entirely on a different planet, this movie handled weirdly complex ideas and pulled them off so successfully it managed to leave strong enough of an impact on Gene Roddenberry to be a key inspiration for Star Trek -- which itself is among the most substantial science fiction works of the 21st century. There's plenty of humor to be found here, tons of great visuals to keep your eyes busy, and a strong plot that keeps your mind active throughout. It's a complete, geniusely crafted film that's among my absolute favorite movies of the 1950s -- maybe even of all time.
Who would I recommend it to? Anyone with even a passing interest in sci-fi. If you can't appreciate it for what it succeeds at and did for the genre, you probably don't actually care about sci-fi at all.