People whinging about fake game girls deserve to be roundly, soundly and mercilessly mocked. They deserve no respect whatsoever, and will get none from me. I like my hobbies becoming more inclusive. I like seeing cute girls dressing up like characters, and if they're doing it so that they'll get a thumbs up from me, more power to them.
In fact, I would much rather girls come to geeks and nerds for their attention needs (if they do need the attention) than to go for studs and athletes, who are far more likely to see the girls as nothing but prizes to be won, used up and then traded in for a newer model a few years later. Geeks and nerds are far more likely to actually appreciate girls trying to please us and more likely to try to please the girls in return, and so it is a better environment for them to try to exist in.
What the difference between that painfully shy 18 year old girl who comes to Comic Con or Fan Expo or whatever dressed as Rikku who is trying to get attention from gamers and nerds, and that painfully shy 18 year old girl wearing a micro-bikini top, a mini-skiry and stilleto high heels with the Michigan Wolverines colours, trying to gain attention from jocks, or coming to a rock concert wearing the same general outfit to try to get the attention of the band? Dressing up as Rikku gives the girl a chance to make a deeper connection to the objects of her attention - she can talk to us about Final Fantasy, about Japanese anime, about video games in general. Or we can talk to her about it, get her to understand what it is about the character we like, beyond the cute outfit.
What does the jock or the rock star have to talk about? How nice her tits are? How nice her ass is? How great she is at blowjobs? Maybe she has an appreciation for football and they can connect about football, or about music and they can talk about how much fun it is to play Stairway to Heaven while people around them are trying to tear their ears off. But let's get serious here - it not likely to be much more than a wham-bam-I'm-done-get-lost situation.