Any good games for a 9 year old?

Plant vs Zombies, Bit Trip runner ( not sure if this would be easy,I must confess I had a hard time at first playing bit trip ), Zuma series.
my other suggestions are 16,17+,18 and M rated games but I don't know if a 9 y/o girl should get exposed to this..

Gianna Sisters, Toki Tori, Scribblenauts, Machinarium, Dust.

The daughter of my sister-in-law has 8years old and played easily this games above.

She prefered to see me playin' Dark Souls and League of Legends. But anyway... I'll take a look into my inventory and update the comment.

Look for easy racing games (like Burnout), BIT.TRIP RUNNER which is addictive...if I remember more I'll edit the post and let you know.

-Fez
-Thomas Was Alone (Would be better if she knew a bit more of English though since the narration is amazing imho)
-Street Fighter/Tekken/any of those fighting games
-Little Inferno
-Giana Sisters
-Fairy Bloom Freesia if she likes grinding.
-Binding of Isaac

Crash Bandicoot & Spyro (with PS1 emulator), Psychonauts, Costume Quest, DLC Quest, Eets, Faerie solitaire, Intrusion 2, Tiny and Big, Rayman... If she want something more easy... Pang or Puzzle Bubble maybe.

Gianna Sisters, Toki Tori, Scribblenauts, Machinarium, Dust.

The daughter of my sister-in-law has 8years old and played easily this games above.

She prefered to see me playin' Dark Souls and League of Legends. But anyway... I'll take a look into my inventory and update the comment.

fairie solitarie, my 9 years old daughter loves it!

Sonic games, like Sonic Generations or Sonic All Star Racing.

emulate a SNES or N64, and get her into mario, starfox and donkeykong !

Dark souls... Prepare to die edition..

Bad Rats? Why....oh, how about Faerie Solitaire? Addicting game...in the end I played it until I got every single achievement.

Binding of Isaaac, Bastion, Plants vs Zombies, Rayman Origins, Serious Sam 1/2/3, Scribblenuts Unlimited, Cloudberry kingdom, Fez, Fortix 2, Dust: An Elysian tale, Guacamelee, Hero Seige.

flappy birds

The Man Hunt games.

The Inner World or some other Adventures, like Deponia maybe..

World of Goo, a good game for anyone with a brain, especially for kids, helping them develop their puzzle solving skills and their overall intelligence. You'll have to walk her through it at first, though.

i got "Pid" for free somewhere and tested it, its very nice a childish. that would be great for a 9 year old :)

Audiosurf

None of these are Steam... but they're the best I can think of (in other words, I'm gonna suggest what I played when I was 9, lol):

I would suggest Re-Volt (classic racing game) or DemonStar (a Shoot 'Em Up of the "Wow, this actually challenged me when I was a kid?" variety- as in, really, really easy)... assuming you can find them, looks like Re-Volt was taken down from GOG. ^_^'
Also Chicken Invaders 1/2/3/4. :D