I have a phrase I use to describe movies, often from my youth, that are better than you might think: An All-Time Classic. It gets confusing, though, because often I use the phrase ironically: "Robot Monster is an all-time classic!" Lately, I've brought up The Beast from 20,000 Fathoms a few times, eliciting eye rolls from my wife, who can't always tell if I'm serious. But in this case, I mean it. I'll just cut-and-paste from what I wrote back in 2010:
This was a favorite of mine when I was a kid, and the surprise is that it doesn’t suck. The effects by Ray Harryhausen are fine, and the script is functional. Of course, it’s harder to appreciate this movie than it used to be, because it spawned so many similar (and worse) ones. But this was the first: the first movie where atomic testing unleashed a monster from the deep, even predating Godzilla. Besides the bomb and the monster, there’s the dedicated professor, the kindly scientist, and the scientist’s assistant who happens to be a woman (and who happens to like the professor). There’s the no-nonsense military man … there’s the monster rampaging through a big city … and then, to top it off, there’s Lee Van Cleef, only a year into his movie career, showing up in the last scene as the sharpshooter who saves the day and kills the monster. I’m sure I had no idea who Lee Van Cleef was when I was a kid, so that’s a nice added touch beyond the nostalgia factor.
Director Eugène Lourié got his start working with Jean Renoir, which is irrelevant but Renoir is always good when you're trying to promote an all-time classic. The movie was as good today as it was in 2010, and as it was all the other times I saw it back to when I was a kid.