I think that's changing. Characters like Carol Danvers and Kamala Khan are proving very popular. And I think Marvel has a broader bench. Maybe they don't have a single female character who stands out as much as Wonder Woman, but DC hardly has any female characters other than Wonder Woman who have comparable star quality, and the only ones who come close are derivatives of male heroes such as Supergirl or Batgirl.
Kamala Khan is doing better than Carol. Carol is going through another rebranding I think. Carol's profile has been expanded to a more WW type role (existing on multiple books in leadership positions) but she's not catching fire like Marvel had hoped. Kamala is doing great with the 60's Spider-Man type story; young teen struggling with her private life and super hero life.
I did have a chuckle when you referenced Supergirl and Batgirl as being derivatives of their male counterparts, because Ms Marvel and Captain Marvel are derivatives of Marvel's Captain Marvel (Mar-Vell). Haha. I know what you meant though.
I'd say it's not so disproportionate though. Characters like Catwoman, Harley Quinn, Black Canary, Starfire, Katana, Zatanna and Raven are very popular and have decent exposure. DC is trying to make Vixen happen, with her web series and expanded role on the JLA, but they've been trying this 06 to do that. Vixen and Hawkgirl haven't really broken out.
At Marvel though, I don't think there is anyone else with the profile of Carol and Kamala. 20-30 years ago, it would've been easy to point to Storm, Invisible Woman, Jean Grey, Rogue, or She-Hulk as Marvel's leading ladies. Today though, the X-Men don't matter like they used to, they keep killing Jean, the FF was cancelled after years of being in decline, and idk where She-Hulk is. The whole Hulk concept has been ruined since they've made so many in recent years.
Both could do better but resources are limited and imagination seems to be limited too. I have ideas, but I don't work for either company. Bummer.