Which rock star will historians of the future remember?

Classifying anyone as the “most successful” at anything tends to reflect more on the source than the subject. So keep that in mind when I make the following statement: John Philip Sousa is one of the most successful musicians of all time.
Marching music is a maddeningly durable genre, recognizable to pretty much everyone who has lived in the United States for any period. It works as a sonic shorthand for any filmmaker hoping to evoke the late 19th century and serves as the auditory backdrop for national holidays, the circus and college football. It’s not “popular” music, but it’s entrenched within the popular experience. It will be no less fashionable tomorrow than it is today.