Interesting that on an audiophile forum, everyone save a few are judging Pet Sounds on how "good" the song writing itself is. The accolades for Pet Sounds have almost nothing to do with the song writing.
Pet Sounds was so different in that it did two things:
1) It was a complete work of all originals: every song, every note every word mattered. The "normal album" for 1965 was a collection of a few orginals and mostly covers. Look at Hollies 1965 for a good example of this. Rubber Soul was one of the first departures from this approach and Brian was a great admirer of this record. This, plus his own creative abilities, had Brian thinking a complete statement. It was quite novel in its day and hard to imagine in todays terms.
2) It was one of the first times a rock artist combined the idea of multitracking and Phil Spectors "wall of sound" into a single project. The super dense complex vocal harmonies Brian created required many many takes (and tracks) to achieve. This was new. He also did this with intruments, layering unusual elements together to create one sound. He even had the Beach Boys play, but then added Wrecking Crew tracks to build on it and make it more complete. Brian approached this Pet Sounds album in an orchestral way, like an orchestral composer does, hearing each instrument seperately yet together, using specific element combinations to create a specific sound. It is very heady work, and requires a big thinker to pull it off. Back in time, classical composers did this. Today its movie scoring composers who do this, like James Newton Howard and Hans Zimmer.
So production and technology and a unique multi element sonic landscape was what made Pet Sounds so different. Its a lot more than if you like songs. THis was a left turn that changed modern recording and recomrd making forever. Sgt Pepper was very different from Rubber Soul, and it is said that it was due to Pet Sounds that the [Beatles] engineering team went to work to figure out how Brian did it, then replicated it.
Brad
NOTE: It might be fun for forum readers to sit down and listen to Pet Sounds and try to hear all these different layers and parts from different instruments. A pro engineer would follow one voice thoughout the song, then another and another. then one isntrument, another and another. This is also how these records are built.