My favorite few:

"Soulful Old Man Sunshine" of course, but it's such a no brainer I'm almost adverse to listing it.  Why?  Incredible jazzy harmonies, I especially like the way the bass vocals perfectly fill out the "soulfullll olllld mann SUN SHINNNE" part, you can hear the bass thump when they say "Sun".  I'm not sure if that's Mike being great, or an engineer being great, or both.

"Walk on By" partially because I like the original very much, and partially because Brian's falsetto is amazing on it.  It's kind of like the wild falsetto on "Do You Wanna Dance?" where it just comes out of nowhere, a couple octaves above the few lines before it.  "Do you Wanna Dance" is really jarring though (although it's good)... but the way he goes up into the falsetto on "Walk on by" is astonishing.

"Big Sur" early version.  It's just very beautiful, very well written, and I'm sure it's just because it's in a minor key, but the background vocals are so melancholy, it's an amazing song. 

"Their Hearts Were Full Of Spring" this would be the later version, not the early early version on the box set.  I would imagine it was recorded around 69 or so.  I like it because it's basically a clinic on harmony.  It's not perfect (some flubbed notes) but it's great. 

I haven't heard all of the songs mentioned on this thread, but I believe these are the 4 best that i'm aware of. 

I'm just speculating, but my understanding of it was that the Brian solo version was just a demo, and a very Brian demo, not a Beach Boys track.  Also they had the incredible production arranged for the first half of the song sitting with nothing over it.  So Carl likely felt that he would love to have a fully produced version of the song, since that backing track is so great.  The piano demo wouldn't lay over the recorded arrangement with the horns and things because of timing differences, so Carl simply resang the first half.  They didn't have any produced 'second half' arrangements, so they just used the Brian demo (not only because it's beautiful, but because it added an extra Beach Boy, a very popular Beach Boy, lol, into the song).  The only other alternative would have been to try and record a new backing track for the second half of the song, or have Carl duplicate what Brian did, or whatever... when all they really had to do is (if your memory is correct) have Carl double a couple spots to thicken it up or whatever, if he did that at all.  Then allegedly Brian caught wind that they were going to release that song, and informed them that the 'child is the father' hook lays over the falsetto outro.  I don't know if that last bit is true but I heard Brian actually helped them arrange that part. 

One of my favorite sources of comedy is Brian Wilson interviews. 


-  The aforementioned fact that Brian actually has sang, produced, released, and likely received decades of royalties for his performance of White Christmas, lol. 

-  I love how Brian answers questions the interviewer didn't even ask.  It's like he knows what the guy's thinking and just wants to get it the hell out of the way.  At the end, he goes "I won't make another album like Smile.  Also; I won't release anymore songs... Also, I won't do another complete album live again" when the guy didn't ask him any of that!

- I like how he puts the disclaimer that he likes all fans 'regardless of social class'.  LOL that's a real weight off my chest! 

- He would like a pair of shoes for Christmas.  That's hilarious, and I don't know why. 

- and my FAVORITE PART of the interview, is how he says his Rock & Roll album will be more like, you know, 60's rock, not 50's elvis rock (as if those are the only two choices).  He's of course right.