We often hear people saying about how a certain artist or composer is better

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We often hear people saying about how a certain artist or composer is better than another. Many people, for example, believe Bach and Verdi to be better musicians than, say, Rihanna or Justin Bieber. I share this same belief, but it is mostly based on intuition than on rational arguments. It is certainly true that Bach was able to develop a musical theme in a much more organized and logical way than Rihanna is, but does it really mean that Bach is a better musician than Rihanna? Is it true that there is such thing as a good and a bad composer or is it all just a matter of taste? Could you point out to me some arguments and readings which are relevant to this type of question?