I think "Good Vibrations" fits perfectly on Endless Summer. For years that song was near the top of the list of songs that "shoulda been on there" including "Your Summer Dream", "Wouldn't It Be Nice" and "Sloop John B".
It's just that "Endless Summer" originally covered 1962 to 1965 quite well which is of a period for the band in a sense. Now on the CD you suddenly skip "Pet Sounds" altogether and go straight into "Good Vibrations" (simply because it was a hit).
I see what you're saying, Roger. That's why I also INCLUDED "Wouldn't It Be Nice" and "Sloop John B" on my "wish list" for Endless Summer. I WOULD NOT have skipped Pet Sounds. If you're going to include "Let Him Run Wild" and even "California Girls", just go one more step and include the 1966 songs.
For me, the cutoff for the "early years", or the "fun in the sun" years, has always been "Good Vibrations". The time period is usually 1962-1966.
I'm sometimes tempted to include "Darlin'" or "Do It Again", but that IS taking it too far ahead...