Hey, thanx for the detailed graphs

and the link to actual gaming usage.
This might be the current overall OS usage but this does not display the revelant information: the installations usage for games. This requires a look at game site surveys like this one from steam:
http://store.steampowered.com/hwsurvey/
Windows = 95.35%
OSX = 3.42%
Linux = 1.16%
Totally different story.
As expected, Windows was and will be the leading monster in gaming industry but did you noticed the reduced usage in all Windows systems? (except Windows 8.1, probably for benchmarks).
This of course doesn't translate to
windows's no good anymore but rather to
other OSes on desktop / tablets increased in share.
The percentages above cover only the OSX installation usage? and say apps on Apple store as well or other growing OS like Android ?
Also, check on the following:
Android is the most popular OS (in recent devices); As of 2013, Android devices sell more than Windows, iOS, and Mac OS X devices combined,[14][15][16][17][18] with sales in 2012, 2013 and 2014[19] close to the installed base of all PCs.[20] As of July 2013 the Google Play store has had over 1 million Android apps published, and over 50 billion apps downloaded.[21] A developer survey conducted in April–May 2013 found that 71% of mobile developers develop for Android.[22] At Google I/O 2014, the company revealed that there were over 1 billion active monthly Android users (that have been active for 30 days), up from 538 million in June 2013.[23]
also:
Originally unveiled in 2007 for the iPhone, it has been extended to support other Apple devices such as the iPod Touch (September 2007), iPad (January 2010), iPad Mini (November 2012) and second-generation Apple TV onward (September 2010). As of June 2014, Apple's App Store contained more than 1.2 million iOS applications, 500,000 of which were optimized for iPad.[6][7] These apps have collectively been downloaded more than 60 billion times.[8] It had a 21% share of the smartphone mobile operating system units shipped in the fourth quarter of 2012, behind Google's Android.[9] By the middle of 2012, there were 410 million devices activated.[10] According to the special media event held by Apple on September 12, 2012, 400 million devices had been sold by June 2012.[11]
Those OSes are not covered by the above usage and they natively supports OpenGL. Of course, the AAA titles are going to swarm all over Windows because this is what people learn't over the years. MACs are are not cheap and this doesn't help game sales, Linuxes, despite the fact they got easier with newer distros, are still not something a new user will consider for his AAA gaming and tablets and such, well, they're small for hardcore gaming.
Conclusion: Windows for AAA titles (and only that)
But could you say that Legend of Grimrock could not be played in one of those OSes as well? I think Almost Human has some plans supporting some tablet OS, am i wrong? Is that wil be interpreted as
installation by above usage?