Yes Pet Sounds is just unbelievable. And Smile is regrettably the greatest lost masterpiece in the history of music - such a shame what happened with that.
After that, I was always of the opinion that everything after was pretty poor, but Sunflower and Surf's Up from 1970/71 were both very good albums. Obviously not at the level of Pet Sounds but critically, those albums were very well received and are well worth listening to and are arguably two hidden gems considering they didn't do much commercially.
Has anyone seen the new film Love & Mercy? Only seen the trailer, but the Paul Dano bits look really good, but the John Cusack bits look naff - for a start, Cusack looks nothing like Brian Wilson.