with regards good and bad music, i will only say that new music can only really be regarded as good after it has stood the test of time. some of it might be around for hundreds of years. some may be ridiculed for hundreds of years, before resurfacing to great fanfare, a la Antonio Vivaldi.
there is much new music i like, but i cannot say that it will survive time. i'm going to see bob dylan and willie nelson on the weekend. but they may not be around in the distant future at all, depending on how culture evolves.
in the end, for me, it boils down to survival of the fittest (): the great Baroque, Classical and Romantic music that still survives in western culture:
Bach, Vivaldi, Corelli, Handel, Mozart, Brahms, Beethoven, Chopin, Debussy, Dvorak, Ravel, Sibelius.