I would think whether you are a fan of hip hop or not that Dr Dre's "The Chronic" or NWA's "Straight Outta Compton" would make the list.
Second, the list is compiled by "experts," most of whom are established (i.e., older) writers and artists, so their tastes skew older. Bruce Springsteen, Elton John...they don't know Nas's music. It's not they're trashing him; it's that the people's whose opinions are consulted for this list are unfamiliar with him.
A list of YOUR favorite albums of all time? Sure. And that's exactly what this is.
The only things really missing from the list would be classical, jazz and opera.
Sure there are always going to be artists that dont appear on these lists that people will question. For me the absence of Queen, Cher, the Bee Gees, The Supremes, Elton John and Tina Turner is questionable.
But then considering the Sex Pistols is on the list as opposed to a massive number of arguably better selling punk groups and Amy Winehouse who was very much a one hit wonder being there in place of the likes of Diana ross or Whitney Houston shows that the list is generally well balanced to most modern western music genres.