Sure, P-521, whatever. I make no claims to accurately ranking curve popularity, except I am pretty sure as a practitioner (not a cryptographer) that the P-curves are still the most popular, and that 25519 and its variants are close behind. Curve448, the Hamburg specification? That's got to fit in there somewhere too?

(I'm not trying to be snarky, just sort of expressing the sentiment of throwing up my hands after having a grip on P-256 and Curve25519).