The "best" portrait artist today is subjective, as it is often determined by personal preferences and the particular style one prefers. In addition to Amy Sherald, Kehinde Wiley, and Elizabeth Peyton, contemporary portrait artists have gained considerable recognition and popularity in recent years. In addition to their unique perspectives and approaches to portraiture, each of these artists has become prominent figures in the field.

A series of self-portraits Van Gogh created throughout his artistic career provide valuable insights into his evolving style and emotional state. In his self-portraits, he shows his artist introspectively and with expressive brushwork.

Several factors contribute to defining a great portrait artist:

a. Technical Skill: A great portrait artist possesses exceptional technical skill in capturing the likeness and details of the subject accurately.

b. Emotional Depth: The ability to convey the emotions, personality, and inner life of the subject in the portrait is a hallmark of a great artist.

c. Innovation: Pushing the boundaries of traditional portraiture and introducing innovative techniques or styles can set a portrait artist apart.

d. Consistency: Consistently producing high-quality portraits that resonate with viewers is a key characteristic of a great artist.

e. Impact: A great portrait artist's work has a lasting impact, influencing the art world and inspiring future generations of artists.

The 19th century witnessed the work of several exceptional portrait painters, making it difficult to single out one as the "greatest." However, one of the most celebrated portrait painters of the 19th century was John Singer Sargent. 

His society portraits, characterized by their elegance and meticulous detail, earned widespread acclaim and left an indelible mark on the art world during that era. His ability to capture the essence of his subjects and his mastery of portraiture made him a prominent figure in 19th-century portraiture.