The following graph is from this great paper by Joel Waldfogel. It tells you what share of the 500 best albums of all time were released in each year. Rolling Stone released its 500 best albums list in 2004. Entries “were chosen by 273 of the world’s pre-eminent musicians and critics ranging from Fats Domino to Moby”. Notice the wonderful 60s, terrible 80s, and short-lived 90s revivals, which included the Pixies, Nirvana, and the Wu-Tang Clan.