The thing is, I'm willing to bet that most of the women who are into 50 Shades know full well that it would be foolish and dangerous to be in a relationship like this in the real world. The thing is, they kind of get off on the idea anyway. Maybe she likes the idea of actually losing control. Maybe she likes the idea of having a powerful man obsess over her, or maybe she's attracted to the danger itself. Whatever. She wants something that's bad for her. I want to dislocate the shoulders of street thugs, even though that's a really bad for me. We don't consume this media because we think it's showing us how to act, we consume it because we know this isn't a good way to act, but we want to anyway.
We're super-smart humans living in a technological wonderland of abundant food, little disease and (historically) little violence. But we're also primates who have spent millions of years killing and screwing to stave off extinction, and you don't negate those primitive drives just because you own an iPhone and an espresso machine.
It's the old cultural tug-of-war: On one hand the puritans are telling you to deny your base desires, and that simply having those desires makes you a Bad Person. Repress them, hide them, deny them, and apologize for thinking about them. On the other extreme are the hedonists, telling you to do whatever you like, as if we lived in a world without consequences. But videogames (and books, and movies, and probably all art) give us a balance between these two extremes. It's a way to keep that inner primate entertained so you can avoid both frustration and destructive behaviors. It's a lightning rod for our vices.
I'll go so far as to say that consuming cathartic media isn't just healthy, in some cases it can be an enlightened thing to do. It's recognition of our desires and an effort to sate them in non-harmful ways.
This is not to say that all media is bad for you, or that there's no such thing as bad art. Or that we shouldn't criticize the message of art. But we could probably stand to be less judgemental of the audience and allow for the fact that we all have our own hangups and our own ways of coping with them.