Some dogs could play fetch all day long, while others have absolutely no interest in chasing a ball. Some might love "find the treat" type puzzle toys and others may completely ignore them. The important things are that your dog finds the toy interesting without becoming obsessed over it, and that it is size and safety appropriate for your dog. A Chihuahua is probably not going to be a good match to a Kong as big as she is, and you wouldn't want to risk having your Malamute swallow one of those smaller size tennis balls.