I remember seeing Todd McFarlane at the Chicago Comicon in the late 1980s. SPAWN was still a new thing, and Todd was talking up how the symbol would one day be as ubiquitously recognized as a black bat in a yellow oval.
I gave it a year, two at the max.
Thirty-plus years later, here we are, with the milestone issue of SPAWN, one issue away from setting the record as the longest-running creator-owned comic, with a wide array of supporting characters, good and evil, and a twisted morality play that treats Heaven and Hell as competing corporations.
I will say that one of the things that made SPAWN intriguing to me was that he had been giving a finite amount of infinite power. Starting wtih 9:9:9:9, every expenditure of eldritch energy caused the Spawn-o-Meter to decrement. Which meant that, at some point in the character's run, he was going to bottom out, and things would be over.