Here is my opinion on the points you raised initially followed by my general opinion about the topic. (its quite an essay sorry, I got carried away, but this is something I spend a fair bit of time thinking about but get berated by my male house-mates for flaming 'hot women')
1- Females in games- I think this is purely as a result of designing games for a target audience, which, while there are lots of female gamers, the majority of gamers (especially serious gamers) still remains to be male. I'm a bit of an RPG nut, and I love the idea of my character being an idealized self (this is more the case for the customizable characters you get in RPGs) who happens to be in a world where you can be a hero and go on grand adventures etc without the responsibilities of life (job etc) or any real risk of injury (if your char dies, you just load). Where I'm going with all this is most gamers are males, and so it would make sense that most game characters would be male, sometimes with the 'perfect (though unrealistic, personality as well as physical) female' side sick / rescuee etc, I think that would stoke most guys egos. Likewise, most main male characters are also unrealistically buff. The fan art is just an extension of this, and possibly that of horny artists (as there is plenty of non sexual fan art).
2- Why are females objectified? Well, because most of us like it. The majority of girls do not have a very high self esteem, they LOVE it when they get attention, especially attention from males (as long as it is positive and not creepy). What is the easiest way to get attention- being intelligent takes effort, having a skill takes time...- the easiest way for most girls to get guaranteed attention is to flaunt their physical assets (you can't tell someone is a mathematical genius or the the worlds best artist just by looking at them). Sometimes this is done in an obvious way, dressing slutty, sometimes its done in a way that is subtle so that it achieves the desires attention without the neon lights. This is just as much (perhaps more) a silent competition between females to out-compete other females as it is to get attention from males. The level of cattiness and competition that exists between girls is usually VERY well hidden from guys (coz were just sweet and innocent right?), thats why there are so many white knights who will jump on anyone to defend the honour of the innocent pretty girl, I'm sure you've all seen this.
So basically, most girls don't mind the objectification, they use it as a standard to try and achieve, but if you are too obvert, then you're being politically wrong and YOU are the bad guy! Look at the behaviours of most girls, the shopping, hours per morning on hair and makeup, self indulgence, celebrity worship and you will see this, treat this girl like the prostitute she dresses as though and fire and brimstone will rain down on you, it's like teasing a dog with your dinner and then punishing it when it tried to eat it. I personally don't like this culture and thus dress is what I consider most comfy / weather appropriate without regard for if it is considered 'hot' or not but then again, I do not like this kind of attention and would prefer to be praised for a skill or ability than simple genetically determined physical features, nor do I try and attract friends by being pretty, I'd prefer friendships based on common interest and personality.
Just my two cents from a girls perspective, hope it sheds some light.