Psycho is a unique and outside of its boldness kind of movie. By that, I mean t the twist ending, and so forth. That was definitely a brave thing to do back in 1960, not only because The Hays Code was still a thing, but also because of the idea of killing off your supposed main cast member.
But Psycho is more than just a suspenseful thriller. Psycho was made on a really low budget , which makes it stand out amongt the higher budgets of Hitchcock's other films which are:
Vertigo: $2.5 million.
North by Northwest: $4.3 million.
Psycho: $800,000.
The lower budget of Psycho meant that it felt much more down-to-earth and more realistic. The film is also notable for being shot in black-and-white, the last time he would do this. Psycho uses the black-and-white to its advantage, by creating gorgeous shadows and a deeply dark, and thus suspenseful, atmosphere, which succumbs to the shower scene.
I also don't know if it's exactly fair to say that a film is "overrated" when you still like it. Maybe it's just me, but I would often say a film is "overrated" when my opinion of it is way lower than the general consensus. Like, if a film has a 4.3/5 average and I give it a 2/5 or something. These include things like The Fly. On the other side, "underrated" means that I love a film a lot more than the general consensus, such as Halloween III. It's a difficult assumption to make, but Psycho is one of my favorite films, and my favorite Hitchcock film, not only for its deviations from the expectations of Hitchcock by 1960, but also because of how it is shot and the way in which the actors behave with the shadows and so forth behind them. It's a genius piece of film for me.