First, the music has to be a good song. A great original song by a mediocre singer or musician can still be good. It becomes great music when the musical performance is as great as the song. A great performance can be good music even if the song is only mediocre, such as Stevie Ray Vaughan playing "Mary had a little Lamb."
Really, good music needs a good song and good musicians playing it. What isn't good music is performers of marginal talent playing formula music, such as market created "boy" or "girl" groups, Britney types, or most rappers who cuss about "ho's" while having no soul or any musical talent whatsoever.
Most popular music is not good. Most is created by talented producers who have the pattern down and can put out a professional composition with the instruments in the right places, find an attractive singer, and fix his/her vocals wth modern technology. There is little soul or edge to most of it, basically phoned in. A lot is absolutely awful. The good thing is a lot of music is made so it is possible to find good music. Most of the best selling music is the worst, that was true even in the 60's.