To qualify as a "best" doctor or hospital requires two things - high volume and substantial research experience. The Cleveland Clinic meets those criteria. Many doctors or hospitals do a volume business (practice may not make perfect, but it helps) but without research they could make the same mistakes over and over. Without the volume, a doctor won't get the judgment that experience provides.

By the way, getting the best results is not always the mark of the best doctor. The best doctors take the sickest patients, meaning the won't always get the best results.