Top TV DVD/Blu-Ray US Sellers Each Year This Decade (from the-numbers.com):
2016 Downton Abbey S6 $14.6 mil
GoT S5 $12.9 mil
2015
GoT S4 $34.2 mil
Downton Abbey S5 $17.2 mil
2014
GoT S3 $40.9 mil
Walking Dead S4 $22.3 mil
2013 The Bible $44.1 mil
GoT S2 $36.5 mil
Downton Abbey S3 $23 mil
2012
GoT S1 $66.5 mil
True Blood S4 $38.7 mil
Big Bang S5 $35.9 mil
Walking Dead S2 $32.7 mil
Downton Abbey S2 $22.8 mil
Hatfields and McCoys $21.1 mil
2011 True Blood S3 $37.1 mil
Big Bang Theory S4 $22.8 mil
Walking Dead S1 $18.7 mil
2010 The Pacific $85.2 mil
True Blood S2 $47.6 mil
Glee S1 $31.4 mil
Dexter S4 $28.2 mil
Glee S1 Part 1 $24.6 mil
GoT will soon be the top regular show 5 years in a row. Impressive that if not for GoT, True Blood would be the top one 4 years in a row. HBO is really good at making people feel like they gotta own the big hits.
I'm surprised at how Downton Abbey's now the 2nd biggest TV show seller. Very different audience than GoT's.
Walking Dead's diehards seem to have faded, while I suspect Big Bang stopped being so big in sales when it became so easy to watch it many times a day on both TBS and syndicated on a local station.