All the dog did for me was bite. I had to be vaccinated against rabies. In addition, they prevent me from sleeping at night, shit in my yard and terrorize children.
Dogs lead the blind, even on crowded streets, and keep them safe. They also allow them to be independent.
Dogs sense impending seizures and let their owners know. And if needed, they will summon help.
Dogs can smell cancer, allowing early diagnosis.
Dogs guard property and livestock. You say they are enemies of cows? Several breeds will guard them against larger predators.
Dogs move herds of animals safely, and keep them away from hazards.
Dogs can track the lost or find criminals by scent alone.
Dogs can find explosives, thereby saving many many lives.
Dogs find drugs that would go undetected otherwise.
Dogs can take down criminals and hold them, without injury (if the criminal cooperates).
Dogs provide companionship and comfort to the lonely and bereft.
Dogs aid hunters in finding and retrieving.
Dogs have transported people and goods for thousands of years.
Dogs have been frontline soldiers, preventing human deaths in war time.
Dogs assist humans with mobility problems, opening doors, picking up objects etc.
Dogs assist diabetics by smelling the telltale odors of low blood sugar long before a human can. And they even retrieve juice or glucose to help them.
Dogs can assist autistic children in many ways, allowing them to better integrate into society.
Dogs can assist deaf people just like they assist the blind.
This is by no means a comprehensive list. But I challenge you to show one other animal on this planet that does as much.