Age of empires is a good game for a car trip.

Pokemon is good if you don't think of it as a children's game, but a 90 hour fleshed out RPG.

Club House Games is good if you have another person in the car with you, or if you just like casual games such as bowling, a dozen of card games, darts, and a total of 42 games.

Any of the Phoenix Wright games are really good if your in to that genre. It's more like an interactive book though...

Diddy Kong racing isn't too bad and it lasts awhile.

Hope I helped...