If another car hits your car while it is parked, that driver's insurance should pay for the damages, unless you were illegally parked and causing a hazard. If the other driver does not have insurance, then you may have to go to court to get him to pay for the damages. Whether or not you have insurance has no bearing on the situation.
Auto insurance provides a person with compensation in the event of an auto accident or other event that results in damage to a vehicle. Liability coverage provides coverage for another party in the event of a policy holder's negligence, while comprehensive coverage provides coverage to a person's own vehicle and property. Only liability coverage is mandatory in the U.S., while comprehensive is strictly optional.
If a car hits another person's car while the car is parked, then the person who hit the parked car is legally obligated to pay damages to repair the vehicle. If the person who hit the car has insurance, then the person's insurance company will make a payment to the owner of the parked car, who can use this money to pay for the repairs, regardless of whether he has insurance.
If the driver of the car that hit the parked car does not have insurance, then he may be in a fair amount of trouble. Not only might the person face civil penalties for a failure to drive with insurance -- this can include a fine and suspension of his license -- but he will be legally obligated to pay for the damages to the parked car out of his own pocket.
Hit and Run
If a driver hits a parked car and flees without providing any information to the driver of the parked car, then he is violating criminal laws against fleeing the scene of an accident. This person is still responsible for the damage he caused, but he will not have to pay if he is not caught. If he is not caught, the driver of the parked car will receive no compensation for repairs if he doesn't carry comprehensive insurance on the vehicle.