Anything that's unrivaled is the very best of its type. If nobody has ever made a more delicious apple pie than yours, your pie is unrivaled.
Some synonyms for unrivaled are unmatched, incomparable, and peerless. Unrivaled things have no rival, or worthy competitor. When a newspaper's coverage of local events is unrivaled, there is no other paper that provides that kind of news. And if a long jumper's record is unrivaled, it means that not only is she the best, but no other athlete has come close to beating her.