Depiction
Sexualized
Objectified
Background
Not there at all
Women are people
They deserve respect
They deserve a story
They ain't just bodies
Women are often seen from a distinctly male heterosexual point of view This is called the Male Gaze. It's a theory. 

The theory suggests that the male gaze denies women human agency, relegating them to the status of objects, hence, the woman reader and the woman viewer must experience the text's narrative secondarily, by identifying with a man's perspective. Google it.
Objectification refers to the practice of regarding or treating another person merely as an instrument. Objectification is an attitude that regards a person as a commodity or as an object for use, with insufficient regard for a person's personality.  
Actually, many male non-player characters are seen as objects as well. Mobs, enemies, cannon fodder.
But they're more often than not non-western and usually a "minority".
Objectification
Language
role models
Gaming experiences
Recruitment
Sexualisation
Background
In many games, women are just a backdrop. Something pretty to look at while playing. Ties in both to objectification and sexualization.
What does this tell players?
Women are objects
They're there to rescue, or to further the plot
Or they're not there at all
(Sometimes sexual objects)
(sometimes to keep the player character from his goal by being sexually alluring. And evil.)
which means that the world is made up from men, and men only. 

Women not allowed.
Talking about women
Talking to women
Telling stories about women
The same kind of sexual objectification that occur in images can occur in language.

Reading about female game characters' "nice rack", "hot ass" or similar can be very dissuasive for many women.  

Women are also often portrayed as passive, while men are described as active and adventurous.
Male-style exchanges often make use of profanity, insults, sexual references, and violent actions. 

Sometimes they contain all of them at once.

Being harassed by someone telling you how much someone would like to use your body, and how, is a definite turn off.

It STILL happens in games, and in discussions about gaming.
Or not telling stories about them at all
Not telling stories about women, and women protagonists, equals females as "not interesting". Being defined as "not interesting" usually turns a person off. 

It also strongly signals "you don't exist in this world. This is not for you."
Talking about women
Talking to women
Telling stories about women
Or not telling stories about them at all
Women don't get the same space as men in or around games. In a game where the storyline is adapted to several game characters of different sexes, the male protagonist usually get most of the attention.

The female story is less detailed. Sometimes it's even impossible to play a game starting with a female protagonist, because the game assumes you've played the male character first.
Gamer status
Game type status
Game experience status

WHAT TO DO?
Create believable female game characters
They don't have to be ugly, but they don't have to have heads bigger than their waist and smaller than their boobs .

Give them a voice. Give them layers. don't use the tired tropes and stereotypes. Don't put boobs on a man either.

Still uncertain? Ask what the female target audience would like to play. Get help from a writer. 
Stop perpetuating the myth that women don't play games
They do. And they like it. Maybe they play different from you. That's okay, too.

Maybe some girls are a) good at playing and b) some are bad. If you really want girls to play more, don't punish either of them by a) trying to beat the record at any price or dis the game as a "girl game" if you can't or b) tell them "girls can't play games".

Instead realise that a) some girls WILL beat you at games. That does not diminish the value of the game, or your performance, or for that matter, the girl b) if you help her instead of dissing her, she'll come back and play again, and maybe even bring friends.
Stop dividing games into status hierarchies
There's a pecking order within the gaming community that reflects a phenomenon that is common in the society at large.

Activities that are seen as "female" have a low status. 

Social games and games such as The Sims are seen as low status, whereas games such as Devil May Cry and Ninja Gaiden are high status. Guess the demographics?

By not placing a specific value on either game experience, more people can call themselves gamers. By expanding the market and by expanding the definition of gamer, more unconventional gamers will be able, or dare, to enter the game industry. From this, we'll see a greater diversity in games.
Good games are universal
They're not pink, black or green. They're simply good games. 

By becoming aware of how women are seen and portrayed - and by changing it - more people will most likely find pleasure in games. 

Now go change the world. And make good games.
"The people who tell the stories defines the culture"
- Henry Jenkins, Moral combat
Promote women in the games business
Women need to see that other women have "made it" in the games industry.

This makes the industry a viable career option. Make sure the women who do work in the industry are visible to other women, particularly women who may want to get into games.

The importance of role models
The importance of female role models (for other females)
The importance of Role models
Role models can be a powerful force for learning and realizing your potential. They’re not only important for your career, but for achieving fulfillment in everything you do. You ought to have role models in every stage of your life.
The importance of female role models (for other females)
One of the factors that inspires more women to pursue specific careers is  having examples of successful women who have done the same. When you are at the beginning of your career and are looking at different career options, men see clear paths and will know several people who traversed each one. They can see other men 20 years down the line. 

For women it is more of a fog. They may not know anyone who has gone that road, or at least no other women. So they cannot visualize where they are going to go, or even which paths are possible.
Recruiting in the games industry
Keeping women in the company
Recruiting in the games industry
How many gaming companies look for game developers with  a passion for games?
Quite a few. Not only does it have to be a passion for games. It has to be a passion for the "right games". 

In an industry that is actively shutting out women by the content they produce, recruiting women can be - to say the least - difficult. Since the industry is also perpetuating the content type by restricting hiring to the "right type of gamer", the industry will become increasingly narrow minded.
Keeping women in the company
It's not enough to recruit. The women also have to stay in the company - not in the least to provide role models for other female prospective workers. 

Considering that the atmosphere is sometimes sexist, this is not an altogether easy task. Considering the content - that some women WILL find objectionable - the job gets even harder.
Gamer status
Hardcore gamers have the highest status in the gaming culture. The funny thing is, there's no absolute definition of what a hardcore gamer is. Some say it's measured in time, others in dedication.

What is even more strange is that a person playing The Sims and creating custom content may not be viewed as a hardcore gamer, even though this person is just as dedicated and spends just as much time as someone doing Unreal maps.

Social and casual gamers are on the lowest rung of the gamer subculture ladder, yet they represent the majority of gamers. They are also approximately 50% female. They spend more time playing than hardcore gamers in some age groups (Nielsen), but they are less respected.
Game type status
This ties in to game type status. There's a very clear divide between "acceptable" high status games- hardcore games - and social games, casual games and serious games.

They differ slightly in content, but usually, the mechanics are similar. 

Social games and casual games are not viewed as "real games", which is a problem, since these are the games that women often play. 
Hardcore games are usually ridiculously difficult (for new gamers), even in the easy mode. They use a language and a visual style that can be (not always though) off putting for the player. Occasionally the game will mock the player if the player fails. Content can also be withheld if the player is using the "Easy" setting. 

These games are directed to a specific type of player, making the audience very restricted. This would have been okay - if there would have been other games to choose from who did not utilize these mechanics.
Game experience status
...which in turn ties in to game experience status. Playing a game on the easy mode is regarded as wussy and girly. 

Getting a good game experience from a game like Bejeweled is not nearly as "cool" as getting a good game experience from a game like God of War.

Women usually play the games that are considered to be worth less in the aspect of game experience.
What's the problem?
How does it all connect?
Games create gamers
Gamers become interested in making their own games
Gamers become game developers
Game developers create games
Gamers see that others have made it
Game developers become mentors
That's how