My 6 year old son begged for a Nintendo DS for Christmas. I just could justify $130 for something that I knew he would break (the whole stylus against the screen would never survive in my house). So, santa brought him a gameboy instead. After all, my husband and I both had gameboys when we were younger and enjoyed them.
Needless to say, he was thrilled when he opened his gift. Santa also brought him a variety of age appropriate games...The Incredibles, Nemo, Lego Star Wars, Super Mario Brothers, and Hot Wheels. He picked it up and right away started to play. He had no problems figuring out how to use the buttons and was better at it than I was. And this is not the gameboy that I had. It's got a color screen and really good sound. It also folds so the screen is protected when not in use.
WE have to be a little careful that my 3 year old doesn't get it, but other than that, he takes really good care of it and it looks pretty durable. He also knows that when he picks out new games he has to get the ones with E for everyone printed on the box.
It was a good purchase for us and I recommend it if your child wants a handheld game but you don't want to spend the money on something more expensive.