DC is only ahead because they have WB backing them for decades. Marvel gives every character a push, as least as far as their books go. Monica Rambeau led the Avengers (granted they were still B-C list), but still...and used their flagship title of Captain Marvel. Bishop had solos, Nighthawk had a solo, Luke Cage/Falcon/War Machine/Misty Knight/Blade had a few. Frenzy got the bump into the X-Men, every decade they try something new with Voodoo, or Prowler. Night Thrasher led the New Warriors, had a book, and recently popped up. There was the incredible Patriot, who for whatever reason is now off the slate. There's everything they've been doing with Blue Marvel. Miles, Riri, Lunella have been all over the place since creation, Storm was in all promo material until they pulled back from using X-Men. There's Manifold, Oya, wack a$$ Gentle.
That's over the past 30 years, while DC was riding Batman. Marvel has done more with Prowler, or even Night Thrasher than DC has done with Mr. Terrific.
You are overstating Marvel while downplaying DC in this conversation.
Monica Rambeau was Captain Marvel when they didn't give a damn about the name and they snatched that title right away from her as soon as it was decided to do a Captain Marvel book with a white alien dude.
For that whole middle section you wrote the counterargument would be Mr. Terrific, John Stewart, Amanda Waller, Vixen, Static, Black Lightning, Thunder, Lightning, Kid Flash, Steel, Bumblebee, Cyborg, Batwing, Signal, Natasha Irons, Power Girl, Kid Quantum, Firestorm, Jakeem Thunder etc who have all had spotlights in team and event books, solo titles or mini-series, one shots etc.
And Mr. Terrific started out being featured in other people's books, became the leader of the Justice Society, had his own solo series, was the lead in the Terrifics comic and is now the co-lead of the Strange Adventures miniseries Tom King is doing. That is more shine than Prowler and Night Thrasher combined have ever had if we are being honest.
Neither company has covered themselves in glory when it comes to a consistent featuring of black characters though. I would give Marvel the current edge just because they have tended to have more ongoing solo titles for black characters recently but nobody is really doing anything worth throwing a parade for.