Famous Pieces
Masterpieces, or even famous pieces of art, often gain this title from their outstanding workmanship, skill, creativity, along with other aspects. These pieces often have to stand the test of time by staying relevant and influential to other artists, but also ordinary viewers.
The pieces here all depict religious and mythological characters, but that is not a necessity to be a famous work of art. The Italian Renaissance is characterized by the importance of Classical art, which centered on their mythology, but Christianity was still largely important.