Eeeeeek, back to the Topic
So, i have my own theory about girls and games.
Letz start with some experience I have with girls and gaming.
My sister for example is a Diablo2 addict.
I was too but there is a great difference about how we played the game.
My sister just loves to play and play and play the game finding new items giving her char a new outfit playing thy story and so on.
When I started to play the game (long before my sister did so ) I was aching for competition. Playing the story was dull for me and i never had the nerve of collecting almost every available set in the game. My mission was to create a char that beats as many other chars as possible in PvP.
The same thing can be experienced with most girls in MMORPGs. While most guys in DaoC ( yeah i stopped beeing addicted to Diablo2 and and CS only to find someting new ) start with RvR = Realm vs. Realm equivalent to PvP only much more massive , as soon as they can get to it, girls are more fascinated by the whole quest thing and storyline. You can see the difference quite clearly in the Realm Points (you get them when you kill players in rvr areas) gathered by toons owned by girls. They are usually much much much lower than with those chars played by guys.
Girls love storyline and making something grow.
Guys like competition and everything that might have a devastating effect, be it on monsters or much better "enemies".