Right, here is a summation of nominations from F1 standard circuits so far (For simplicity and consistency with the idea of this thread, I have included Fuji - which is up to F1 standard - but none of the other 'non-F1' tracks).
These are the nominations, in rough order of merit (since I did not include a poll, there is a degree of interpretation in the postings of this thread)…
Roughly equal enthusiasm was shown for Spa, Suzuka, and Silverstone; with Monza and Interlagos coming up next. Behind these were nominations for Monaco, Fuji and Nürburgring.
So, here's a subjective attempt at being objective!:
Equal 1st are the 'S's:
Spa
Suzuka
Silverstone
In equal 4th, we have:
Monza
Monaco
Interlagos
'Also-rans' were:
Nürburgring and Fuji
Conclusion:
If Spa is no longer absolute King, its popularity with participating not606 members suggests that in general, we still regard it as a prominent Royal !