in terms of music history, and knowing songs rather than albums, I don't think it necessarily matters that much when you were young. Just because you didn't buy an album at the moment it came out doesn't mean you can't familiarize yourself with a band through albums rather than individual songs twenty or fifty years later. Like many people who were growing up in the nineties, I may have a certain nostalgic attachment to crappy nineties pop, but I far prefer the music of the 70s and 80s, before or around the time of my birth, and in many cases that includes entire albums or even series of albums.

By the way, as for music genres for the next quiz, my vote would be progressive rock. I'd say 'or metal' but my metal tastes are a lot more limited to specific individual bands and I'd probably do very poorly.