It is difficult, if not impossible, to definitively name the best musician of all time, as music is a highly subjective art form that evokes different emotions and resonates with people in unique ways. With that said, many might make a case for influential and iconic artists such as Wolfgang Amadeus Mozart, Ludwig van Beethoven, or Johann Sebastian Bach. In more modern times, revolutionary musicians like The Beatles, Michael Jackson, or Freddie Mercury could be in the conversation. Ultimately, the concept of the "best musician" is open to strong debate.

This question's ambiguity stems from the fact that it doesn't provide any specific criteria by which to evaluate and compare musicians. To determine the "best" musician objectively, one would need to establish clear metrics, such as technical proficiency, innovation, influence on other musicians, commercial success, or critical acclaim. Even then, weighing these different aspects against one another introduces an element of subjectivity. Additionally, the term "musician" is broad and could encompass singers, instrumentalists, songwriters, composers, or even producers across countless genres and eras. To make this question more precise, one could ask, "Who is the most influential rock guitarist of the 1960s based on contemporary reviews, album sales, and noted musical innovations?" While still open to some interpretation, this refined question establishes a clearer framework for evaluation.