I have an iPhone and the kids have iPod touches so we play a lot of games on those. One of our favorites while traveling is Trivial Pursuit. My wife controls the phone and when it is my turn she "rolls" the dice, tells me my category options and asks me the question. When it is her turn or the kids they pass the phone around and take their turns. We also have Monopoly and Yahtzee.
In some ways the board games are more fun, but the electronic versions are very convenient.
Last time out i was playing Yahtzee at the dinette with my wife, daughter and youngest son while i played Trivial Pursuit with the oldest while he was on the couch.
Beyond that i am completely addicted to Bejewelled Blitz for Facebook and the iPhone