Such a landmark, it's hard to assess
This movie is Hitchcock's most iconic, one of the landmark films of all time. That makes it difficult for me to evaluate. I can't quite get back to my impressions on first viewing it decades ago. Even then, there was so much generally known about the movie that the complete experience was compromised a little bit. Those first theater audiences got the full effect of seeing something new and unexpected. It's kind of like trying to make all-time top song lists. Marvin Gaye's "I Heard it Through the Grapevine" belongs near the top, I think. It was thrilling and wonderful when it came out. Now, I'm tired of it and don't long to hear it again.
Still, Psycho has much to appreciate, particularly Anthony Perkins' Norman Bates and Hitchcock's direction of the lead actor.