There's a game called Whale Trail on iOS that everybody loves. It's free and it hooks people of all ages with it's fantastic graphics and catchy music (and no ads!).

It's basically a game where you're a whale that's flying through the sky, and you have to avoid hitting the electric clouds. You press on the screen to go up and you stop pressing to go down. There are fun power-ups and little tricks you can do. It's difficult to describe, but check it out!

I think people love how intuitive it is. I had my iPad in my back seat and twice now I've had college students get hooked on playing it while we drive!