Alice explains what's going on here -- it's not merely sexism at work, it's something much more insidious, because it's much more baked in and invisible. Fundamentally, people hang out with people who are more or less like themselves. Thus, when you ask people to name the most important people they know, they start with the people who are already in their minds, and those are usually people they see on a regular basis. Fundamentally, women aren't part of the gamer boy's club because women aren't part of the gamer boy's club.
The reason women aren't currently making up 50% of every field is not an intellectual issue, but a cultural issue, and the longer we continue to publish lists containing all-men or nearly-all-men, the longer we propagate the broken image and insulting idea that women aren't as good, or as important, as men.A long way to go.
Many women just haven't had the chance yet: they haven't had the encouragement, the education, the freedom, the support, the role models, the contacts, the friends in high places, the opportunities and the finances that their male counterparts often get by default, by tradition and by homophily.
It's not right and it needs to change. Monocultures are evolutionarily a dead end: game people, take note.