Recommending a game is hard with so little info. Are you planning on using a wheel? Controller? Keyboard? What platform? Looking for realism or arcade? I'll try my best giving some recommendations
Arcade: Dirt 4, Project Cars 2, every NFS game, Forza Horizon 3, etc are some games that even little Timmy can play after coming home from kindergarden. Easy to learn, easy to master. You get my point, these games are made to handle unrealistically. Even though the objectives in-game can be challening the handling itself is very kind.
Sim / Simcade: Dirt Rally, Assetto Corsa, Richard Burns Rally (With NGP mods ofc), just to name a few. Medium to learn, near impossible to fully master. These are significantly more realistic and thus harder. Expect to crash very often in the beginning. You'll get a superior experience with a FFB-wheel but you'll still have fun with a controller.
My recommendations: Dirt Rally and Project Cars 2. You'll get a sweet mix of both worlds. If you can only get one now I'd say go for Dirt Rally. It's not as hardcore as Richard Burns Rally but very realistic overall.