Johnathanamz: I would actually like gog.com to offer a feature like this to video game publishing companies, video game development companies, and indie video game developers.
Mnemon: That, however, won't necessarily give you a clear indication of Linux use, either. I exclusively use Linux for years now, but still buy Windows only games on here, given how good emulation though Wine on Linux has gotten by now (at least for quite a number of games) . PlayOnLinux alone has, right now, around 270* automated install scripts specifically for GOG games - a decent amount of the catalog. It's likely that if you tinker around you can get quite a few more working. Add dosbox and ScummVM, which run fine on Linux, and there's even more out there.
[* I might have miscounted - came up with 271 - it should be there abouts :) ].
I'm afraid I'm going to have to disagree with "good emulation on Wine." Wine is rather crap. It can run a few games but I had trouble with both new and old games. There are few games I can get working and fewer that I can get working properly.
shmerl: For GOG, sales data isn't enough, since if games are cross platform - you are buying all versions at once. What makes more sense is may be statistics of downloads per OS.
What if you like downloading all versions. Or what if you use GOG like Steam and only download when you want to play.