Is it "games" or "activities"? What's the age range?
My girl likes different video games to my boy. I don't know your budget but she likes (Wii) "Boogie Superstar", Wii Music, Wii Play, whereas Pete just likes to race stuff and shoot stuff. Mindyou, if you had a Wii they would probably all get too caught up in making their Miis for the first few sessions.
I am a serious knitter, so I would probably try and set up some knitting lessons in a small group. I have taught Siobhan and one of her friends to knit and I was quite surprised at how they would merrily sit, knit and chat like a pair of old ladies. Oh wait. That's not a game...
Polly pockets were popular when she was younger and they are great for fine motor and social skills (but the tiny parts get lost very easily).
Obviously, board and group games like monopoly, battleships, scrabble, Jenga, ker-plunk, boggle, Operation etc. (just had a peek in the games cupboard).
ASD girls often like things like Pokemon and Bakugan too.
I hope this helps.
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"Clue" is a big one here (OK I have a boy but he has girl friends). How about "Apples to Apples"? There's a Junior Version that is a little easier in terms of knowing the materials.
And yes, video games are just as big with girls as with boys.
How about a station to decorate cupcakes or cookies?
If your thinking of board games, Chess might be a good one for both Girl and Boy Aspies.