Before we do feed it, I'd just like to get a word or two in. Yes, women are depicted as stereotypical sex symbols in games, but so are men. The difference is that while the women are depicted that way to draw in male gamers, men are also depicted that way to draw in male gamers; the target market is men, after all, and what better way to get them in than by both appealing to their egos and their penises?
Even in games with fleshed-out characters, those characters are still hardly realistic, so I'd say a lot of it has to do with simple entertainment value. People want to see cool guys doing badass things, because that's what society says a man should be, and people want to see attractive women posing seductively, because, unfortunately, that's what society says women should be. It's the same thing with fat people, who are depicted as lazy, often dishonest, jolly, or irresponsible.
The problem with all of this, though, is in how this difference is treated; namely, just as fat people are often implied to posses certain traits because they are fat, so too are women implied to possess certain traits because they are female. And, of course, these "female" traits often involve being passive objects, weak, etc., the opposite traits of course belonging to men, who are active subjects, strong, aggressive, etc. Naturally, the "male" traits tend to be favoured a lot more than the "female" ones, and this is where the debate lies: not in that the traits themselves are good or bad, but in that when they are possessed, they are often ascribed to that character's gender.
Besides, when's the last time you saw an unattractive female lead in a game? I mean "unattractive", too, not just "less than supermodel standard". I can think of plenty of male characters, but not a single female one.
