The Beach Boys are a very special Group to me, as not only did I already love them ("All Summer Long" in particular), they were the first I saw live (in the Summer of '64). But Brian Wilson is even more so, being the greatest songwriter of his generation imo (Paul McCartney may agree, as he names "God Only Knows" as his favorite song of all time. I'm not a big fan of Paul's, but on that we agree). When TBB started making them in '61-'62, albums were just a hit single or two with lots of filler. Not just BB albums, ALL Rock n' Roll albums. One of the reasons Pet Sounds is considered as important as it is, is because it was the first Rock n' Roll album conceived and created AS an album---every song was an "A", no filler. I have never liked it as much as I am "supposed" to, but it was hearing Pet Sounds that inspired McCartney to also do an all "A" song album, Rubber Soul.
And it was hearing Rubber Soul that inspired Brian, being a competitive kinda guy, to create "Smile", the first Rock n' Roll "concept" album. Recording commenced in '66, but the album was never completed (for reasons too complicated to go into here). "Smiley Smile" was released in its place, and was a huge disappointment to all. Brian went into seclusion, not fully reappearing for many years.
The Beach Boys (basically without Brian) subsequently recorded and released a few more spotty albums, but it wasn't until they left Capitol Records (who were still promoting them as "The Number One Surf Band In The World!", this at the height of the psychedelic/hippie era. Surf---how cool ;-) and signed with Reprise Records (a Warner Brothers label) that they came roaring back with "Sunflower", a great album. As is "Surf's Up". Those two, I agree fjn04, are probably their best. But the "Smile" recordings were finally assembled into their somewhat originally-conceived form and released a few years back, and the double-CD "Smile" album is an essential album for Brian Wilson, at least, fans. It is quite amazing.