What is "good" music?

If you're to compare artists, they best be from the same time frame ; Renaissance Era, try Leonardo da Vinci who worked on the Mona Lisa in comparison to Donatello Buonarroti, who worked on "David" and "The Separation of Sky and Water", etc. The comparisons have to be near the same time era, or else it's unfair and not only that, but it'd have to be two famous works. Basically what Spidey said, always beating me to the punch.