My 5 year old son absolutely loves Machinarium

The most amazing thing about this game is how much my 5 year old son loves it. He has played the game through dozens of times and still plays it once in while. The only point I have to help him get through is the "5-in-a-row" puzzle. The storyline speaks to a child and my son actually understands the concepts of being lonely and being bullied by the big guys. He has so much empathy for this poor little robot. He can talk for hours about how we're supposed to help the little guy. It makes me proud. The point is that unlike almost any other game you don't have to be able to read english to get the idea. The characters express their feelings without words.
I recommend that you play this game with your kids. It's non-violent, logical and sweet.

For those of you with access to a Wii console I also recommend "Pikmin 2" which is also a great game to play with your children. Again my son absolutely adores that game because of the cute beasts and the storyline.