Since today is TBT I thought I'd give Google Music a chance to impress me with it's selection. I checked out GM's 00's selection and it seemed focused on some form of rap & pop. It looks like a Justin Timberlake, Snoop Dog reunion of sorts. Then I tried 90's and that was almost completely dominated by rap. When I got to the 80's I found one that was considered electronica and 2 others that were dominated by Michael Jackson.
First of all, if I were a country star I'd be pretty pissed. Even though I'm not a true fan there is plenty that I would listen to like a selection of Garth Brooks; and there are plenty of others. Punk and Metal were totally absent. I could be suggesting that either Google knows it's average user but that it does not know my taste.