I think the truest test of a golf course's quality and architectural merit might be whether or not its designer -- i.e. the architect who actually designed and built it -- would happily be willing to play it every single day for the rest of his life.
I'd bet that, if he had to, CBM would've been very happy to play NGLA every day for the rest of his life. I bet the same could be said for Crump and Pine Valley, and MacKenzie with Royal Melbourne (and maybe Alwoodley and Augusta and Pasatiempo and Cypress Point etc).
We could go right down the list of all the old dead guys.
Of course, I don't think we could ever get an accurate and/or honest and/or definitive answer: the old guys are dead, so we can't ask them; and our moderns -- all of them -- would just have to say yes, and yes to every single course they have ever built -- and so it's no use asking them either.
But, in theory at least, I do think that this would be the truest test of a course's architectural merit -- not, please note, because the collective deemed it to be of merit, but because its individual creator would've obviously designed it to suit his own truest tastes/ideals, which in and of itself would be both the course's merit and its raison d'etre.
Needless to say, I've played one or two courses by one or two designers who would never, I don't think, willingly play the ugly torture chambers they'd created every single day of their lives. On the other end of the spectrum, I'd bet that old guys like Colt and Park designed dozens of courses that, if they had to, they'd happily play every day for the rest of their lives.
Peter