As an industry, we still clearly have a bias towards males characters, with 90% of all video games released in the U.S. and Europe on seventh generation consoles having playable male characters. However, that 51% of games this generation have playable female characters is an incredible accomplishment for our industry and reinforces our progress towards serving ever widening demographics. Even when core (Action, Shooter, RPG, etc.) and casual genres are separated, the percentage of core games with playable female characters remain at a respectable level, while the male/female ratio in casual games reaches parity.
The article goes into detail on how the quality of reviews for games that feature a female playable character are not impaired or different from other games. It also mentions how top 10 NPD titles can't really reflect this as the top-selling games tend to be either of an iconic nature (sports, mario) or war and combat, where women are traditionally not at the frontlines.
I'm glad that someone went and made the statistical analysis of this nature to show how far games have progressed in the current generation of systems.