Unprecedented level of stats for Steam game sales, all time lists for 2008-2015 data, breakdown for individual years, and even few sale stats for games that were removed form Steam:
http://www.neogaf.com/forum/showthread.php?p=158851549
At last, the great mystery of how much sales happens on Steam is unveiled.
Also note that it's the same method as Ars, so with the same +/-10% error margin.
However, as noted by some in that thread that doesn't take into account games that have been removed from sale. For example.
It only lists Deus Ex: HR Director's Cut at 1,004,603 +/-54,454.
However, before Deus Ex: HR was removed from steam it was at ~2,116,073 +/-10%. (not on million sellers list)
Even worse is Metro: Last Light. It's not even on the million sellers list. However, before it was replaced by Metro: Last Light Redux, it had sold ~1,308,481 +/-10%. Redux is only ~188,741 +/- error margin.
So, it's interesting, but don't put too much into it. But it does show that software sells really well on PC. And there are a lot of million seller titles that aren't in that list because they've been removed from sale.
And already this year (only 1/4 of the year so far) 522 games have been released on PC.
Regards,
SB