Who are the best artists throughout history?

There are many artists throughout history and across different mediums such as painting, sculpture and photography among others.  Some of the most well known painters are Leonardo da Vinci, Rembrandt, Claude Monet and Salvador Dali.  Donatello is one of the most famous sculptors working with materials such as marble, bronze and wood.  Michelangelo is a famous artist known for both sculpture and painting.  There are also many famous photographers throughout history including Ansel Adams who is knows for his portrayal of nature.