Both. Sturgeon's law applies: 90% of everything is crap. But if there's more stuff, that 10% that's good is going to be bigger. See also: the explosion of d20 material in the early 00s spurred on by enabling the licensing of D&D material on extremely generous terms, which is pretty close to putting D&D in the public domain in its effect. There was a lot of crap, a bunch of serviceable material, and some real gems.The most creative, in terms of quantity, or quality?
I don't need to establish that it's "more creative". I only need to establish that it fills a very well-regarded niche, which is clearly the case. It's a successful and critically acclaimed comic, and there's even been a movie made based on it.We already have more creative works, in quantity, than can be be consumed by the market. And you've not established that League of Extraordinary Gentlemen, for example, is specifically more creative than an original work.
The public domain is filled with characters with which we are all familiar, and that can be easily appropriated to your own story. Merlin, Cinderella, Robinson Crusoe, Dracula, Robin Hood, Alice, Ariel, Puck, and the list goes on. There is no reason Superman, James Bond, The Moomins, Pippi Longstocking, Blackadder, the Doctor, Jim Kirk, Spock, Rincewind, Granny Weatherwax, and other creations of the 20th and 21st centuries should not be allowed to join that public domain pantheon.
I also find it particularly galling that Disney is leading the charge to extend copyright given that they made a significant portion of their wealth by providing their own interpretations of public domain stories and characters. Disney gets to make movies based on Snow White, the Jungle Book, Pinocchio, and Oliver Twist, but we can't publish stories with Scrooge McDuck, Luke Skywalker, or Spider-Man.