There is never just ‘one best’ imo because people have different music tastes.
Top is about what the corporate industry is pushing. If you go back to the 1940s, ASCAP wouldn’t even publish Rhythm & Blues recordings (handle publishing rights, it’s different than the actual pressing of the record) or Country music (at the time the were referred to in the industry as “race” and “hillbilly” recordings).
BMI would publish these recordings.
Atlantic Records changed “race recordings” to rhythm and Blues (Jerry Wexler’s creation?). Don’t know who got them to stop calling it “hillbilly”.
Later, when rock and roll came out of rockabilly and jump blues, ASCAP still refused to publish it and then decried the “payola” in the industry that had always been there since the 1800s and is still there today. ASCAP couldn’t control the top songs anymore (because they had sufficiently rejected a large untapped part of the marketplace) and so they alleged criminal conspiracy rather than willful neglect on keeping up with the public’s tastes.
The same is true today as the industry blames their falling tv, movie, radio, and album sales shares on “piracy” rather than a Big Media empire that would rather dictate than respond to public taste.
“Top Artist” is determined by Billboard or other tracking chart rankings on sales and airplay (in the right markets). Has nothing to do with quality or public taste.