I'll list two here:
Plants vs Zombies - 9/10
For what it is, Plants vs Zombies is just about perfect. Entertaining enough for me and my other late 20's/early 30's friends, simple and cute enough for my 10 and 12 year old nieces.
And Yet it Moves - 8/10
Another very simple game, but captivating fun. You play a paper guy, roaming through worlds in which you have control over what "down" is.