UNO, from Gameloft, is an old-time card game that's especially ideal for families with children. The rules are simple, at least for the standard game. I know many adults who play UNO as well, although I don't think any of them are brain surgeons or rocket scientists.
iPhone and iPad apps tagged "family games."
Bounce and Splatter Your Way to Fun With de Blob
An innovative and fun platformer makes its way to the App Store in the form of de Blob. If you are a Nintendo Wii owner it may sound familiar as it also exists in a well-regarded Wii version. The developers made good use of transforming it from one motion-sensing gaming platform to another.
Disney Fairies Fly Soars to Graphic Heights on the iPhone
Forget about a theater near you, Disney's Tinker Bell movie takes to new heights with the new iPhone and iPod touch game Fairies Fly. While not for everyone, I can think of quite a few folks who will enjoy this simple-to-play, gorgeous-to-view app.