So best music means most successful music so Justin Bieber is the best musician in the scene right now?
No... I mean that if you are going to determine the best SINGLES, then popularity and success are factors. Single means released to mainstream radio. Best song would be a totally different story and not based on popularity at all. The connotation of the word single implies that bands are trying to market the song, therefore their best singles are the ones that marketed the best.