Here is a 2013 longlist. These are albums, in alphabetical order, that i'm considering for the 2013 list.
I like what I see...lots of diversity in genres, and a decent balance between acclaim vs. popularity.
A couple suggestionsCzarface - Inspectah Deck, 7L & Esoteric
High critical acclaim. Decent Popularity (# 35 on Billboard 200). Highly respected in underground circles.Southeastern - Jason Isbell
This is probably the biggest omission from your 2013 longlist. Southeastern
was recognized as one of the best singer/songwriter efforts of the year. See pitchfork for a spot on review http://pitchfork.com/reviews/albums/18283-jason-isbell-southeastern/
Also, lets not forget popularity (peak #6 on Billboard top Rock Albums & #23 on Billboard 200)
Acid Rap - Chance the Rapper
This was a mix-tape. http://en.wikipedia.org/wiki/Acid_Rap
I don't see why mix-tapes should be excluded per se, however if you're going to include one, it would make sense to be consistent and apply the same criteria for years 2010-2012 as well.