Re: Spider-Man. And I'm going to drop the spoiler tags now, because it's unlikely that there's anybody left who doesn't know at this point.
Byrne brings up a valid point, in his own extremely John Byrne way:
More creative bankruptcy. Remember the Black Panther? Remember Luke Cage?
Somewhere along the line -- and, sadly, it's not recent -- Black characters at Marvel suddenly were only allowed if they adopted the names of existing characters. Iron Man. Captain Marvel. Giant-Man (who'd begun with the staggeringly original name "Black Goliath"). Nick Fury. Now, a Black Spider-Man.
I'll admit to having created only a handful of Black characters, but at least NONE of them were forced to follow in some White guy's footsteps.
Aren't Black audiences weary yet of this modern-day Minstrel Show?
And that got me wondering: what non-legacy superheroes HAVE gained mainstream popularity in the past 20 years?
Here's what I came up with:
Static
Spawn
Hellboy
The Tick
Gray areas:
Blade (created in the 1970's, got a movie in the 1990's)
Savage Dragon (had a cartoon, I don't think it was that popular)
Mysterymen (had a movie, ditto)
Kick-Ass (ditto, and as the most recent it's a bit early to tell what its staying power will be)
New Teen Titans (not sure if this counts as "non-legacy"; Starfire, Raven, and Cyborg are non-legacy characters explicitly created for a legacy team book)
First of all, it's interesting to note the number of minority characters on the list.
Second, it's also quite interesting to note just how many of those are creator-owned. (Or at least were originally. Does DC own Static outright now?) I think, as much as anything, that points out the real inertia in the Big Two -- it's not that people aren't creating new characters for them; they are, all the time. But I think people who read DC and Marvel are probably less likely to buy books featuring new characters. And even out of the ones who become popular, it's rare for any to be worth the risk of a jump to TV, let alone film. (Though if the Deadpool movie gets made, he'll go on the list too.)
Blade's the real outlier; he's an obscure 1970's character revived for a film franchise a couple of decades later, right as Marvel was coming off of bankruptcy and right after Batman and Robin poisoned the well for superhero movies. It was a comparably low-budget, low-risk venture -- and so were most of the rest of the movies/shows on this list.
So, people ARE making new shit. And a handful are making POPULAR new shit. But most of those are doing it outside the DC/Marvel framework.