>>5760If you want a nice history lesson about the (popular)songs, go and watch the weekly rankings FROM THE BEGINNING.
http://vocaran.jpn.org/is a good place to start. Every video is ~30 minutes, but it's enough if you only watch the "Top 30" segments.
If you do this, you'll notice how much things and quality changed over the years. It feels like a small time travel into the past. It might take a long time, but I think it's worth it.