What does "good" even mean? Everyone, regardless of whether they have a penis or vag, is usually good at some games and not others. I suck balls at MW2, but I'm pretty good at Left4dead. Then again, there is ALWAYS someone better, so you'll always suck to some people. Just the same there is always someone who sucks worse, so you'll be like a god to them. Gender is irrelevant.
In my experience these threads are usually created to draw attention to the fact that "Omg Imma gurl and I kick ASS in Mw!" so when I see one I can't help but roll my eyes. This topic is a dead horse constantly being revived, and it needs to freakin' die.
Seriously, everyone needs to stop bringing it up and let us play our games in peace without having attention called to our vaginas. (funny how a chick usually starts the thread)
As for the original question: Yeah, probably. I play online a lot, so who knows who the hell is on the other side of the screen? And my best friend is really good at RE5 -- she kicks ass in Mercenaries. I mean, she's the type to obsess over score and crap, so she does that with pretty much every game. I usually don't care at all, so I don't try as hard and end up dying horribly. I'm not even gonna' come here and say, "Well I'M one of them!" because there are too many damn games I've played/sucked at/did okay in/did good in/did really good in for me to even label myself a "good" or "bad" "female gamer".
Also, does it MATTER if they're good? Does it matter if ANYONE is good? I think as long as they're fun to play with then they're cool.
That's just my opinion though.
And no, I was not trying to be offensive or anythin'. It's just my own opinion.