I thought that a little strange as well. And way too much hip hop / rap from my point of view. Also grunge. There are vast swaths of musical genres not even considered in any of this entire list, which is unfortunate, not to mention many very influential & talented artists who had monster albums, even if it wasn't in the USA. This whole list was totally, and I mean TOTALLY geared to "today's" Rolling Stone magazine male / age range target demographic.
In essence, I found it to be very shallow, way too opinionated and not opened to the musical world except the little 1/8 pie slice that they focused on.