Temperament, not breed, makes the rescue dog
There is no single "best" breed for search and rescue - individual temperament matters. A good rescue dog has strong motivation for food or toys, balanced nerves, sociability, stable energy and a willingness to cooperate with people. Common breeds are the Malinois, German Shepherd, Border Collie, Labrador and Golden Retriever, and for individual scent trailing, the Bloodhound - but mixed-breed dogs can excel too.
This page first explains the three qualities that really decide, then goes through the breed profiles and shows you how to test at home whether your own dog is suited. For the big picture, go back to the guide on search and rescue dogs.