I have noticed that female players vary like male players. Most like being skillful and kick ass. Most females really hate system that forces them to play "females roles" and get sub-par stats because of that. Male players tend to have more female characters in those systems than femele ones, if allowed.
You really can't make game for gender. Maybe to some culturally brainwashed little girls and boys but that really goes before people start playing rpg:s.
Curiously I've noticed that many females including me kinda like named magic items. Some unique name for sword/armor etc and some little quality more than +1 to back it up is something really cool. Appearance of gear is secondary to that. IME females and males pay about same amount of interst for character looks, some are all over such little details, and some coudn't care less, as long as stats are ok. Apperance likers are ones more likely to hide helmet/shouders in World of Warcraft MMO even if they otherwise wear things that look crappy just for stats.
There are about same amount of femele min-maxers than males.
Most female players have one female friend that also plays. And they almost always pair up as type A and type B personalities. B is the one that just doesn't learn the rules and relies on other people what to roll. A-types are there to play rpg, B-types often socially hang and often get datinig someone in the group. I say often, since IME it has been pretty damn common.
Avoid any "special rules" for girls. They exist to screw us up. No only-for females rules, unless you wish to make rules about pregnacy and childbirth, which might come up. In last game I played that caused so many stupid arguments I wish there had been rules.
And with that never ever force that on character. It's annoying and should happen anyhow on personal (not-adventure) time.
If you can't be mature about such things avoid such rules altogether.
I recently got into this new group that uses highly vulgar language and tells nasty in-game jokes. I am fine but I wouldn't ask my sister to play with these guys.
Best kinda roleplay system for femeles is guite gender-neutral one. Sure it can have sexy things, I meant in way system doesn't differiate sexes a lot, but allows players to do that if they want to.
Also system should support more combat focused game and more story-focused game equally White Wolf games did that quite well, even if rules kinda, um, failed sometimes.
Don't assume that all female gamers come from same mold.
Also make the universe you write have some interesting qualities. Basic D&D universes are kinda boring. We have seen those. If you want to attact new gamers in any system use some old that works and add some new to get people interested.
Also, we want "awesome powers". Most femeles dislike realistic historical simulations. There are those out there too, but they often have picked different hobby than rpg:s. Fsntasy is supposed to be, like, fantastic. All females I play with give you roll-eyes if its called "dungeons & dragons" and doesn't have real dungeons and no dragons. Femeles tend to draw deep conclusions about impressions.
And we don't play games like Blue Rose. First of all its too uh... not really avarage female idea of cool/romantic. Plus the world was lame. Girls who are into relationship/romance fantasies do that with books/movies/famious unreachable people. White Wolf game worked because it was game about violence/politic/relationships of supernatural horrors. Who looked hot or at least bad-ass. But were not weak or vunerable. Or petite and virginal. You were crusider fighting for your purity if you were that, within system that was thinly veiled laws of the jungle. And those games had lot of example character types ripped from movies/literature and they had inspirational guide for books/movies at end of each book. And it world similar to this one.
Roleplaying is however quite quiet where I live, no more new players, and if, they are rare and often related to oldie rpg-players as their kids who maybe recruit some friends or just play with pap and hide the shame.
I think we need new coming of rpg:s if we want more of anything to like our games. But there is so much compettion for our time now and roleplaying games take lot of time.