I don't believe this assumption from the 90s anymore that the users are just forced by market power to use windows or the preinstallation problem as main reason for the minimal adoption. And that if the users would be brought in contact with linux (like it is now!) they would love it and instantely migrate. I believe the main problem for linux ... is linux itself. The inability to overcome some legacies like the unix roots and being still developer/hacker focussed (users don't want and don't need to become hackers... linux has to adapt not the users). Or the inability to unite the distros and form a linux platform. The missing long time binary comaptiblity. The missing of a unified and standardized multimedia framework (some DirectX alternative (no OpenGL is not enough)), the missing standardized GUI API ... Described recently by several linux gurus ... e.g. Molnar

Windows bundling problem from the 90s didn't go anywhere, no matter how weird it seems these days. If you go to any Dell / HP whatever on-line store and try buying any model without an OS or with a free one, you'll get nowhere (try it yourself and see, it takes just a minute). Only very few models if ever have such options. However it can differ in local stores. For example in China the situation is much better with free OS options for consumers.

GOG could just try it and sell the Linux versions they can get easily and then they would get a more insightful estimate of how much they could earn with selling Linux versions.

We can say what we want, in the end it is GOGs decision alone and we'll never guess the right number of potential Linux buyers, since this is just some prediction about the future and nobody knows the future exactly.

My feeling is that in the end you just have to try it out to see if it works and since the costs of offering the Linux version which are there are so small, but the benefit in reputation and potential profits is real, I would do it.

But it's their decision. If they want to invest their money somewhere else in the Windows/Mac or whatever world.. I understand that too.

And with Humble Store as potential competitor offering DRM free Linux games.. there is a place for Linux gamers too.

Despite you think it, OpenGL is a really fair competitor to Direct X, especially considering it runs on pretty much every platform. Don't forgot that OS X don't run Direct X too, nor Android, iOS and so on. Actually, something already running on OS X don't require lots of works to run on Linux as origins are similar.

And about the preinstalled windows on sales is a real problem. I'm at university and we use Linux every day, we know it a lot. But UEFI with secure boot required by Microsoft and dual boot possibilities because of Microsoft's egoistic behavior are really a problem in these cases.

Lastly, the "non-unity" of distros as about desktop environnement as it seems you're unhappy about this and think it's a problem, NO it's a strenght because it bring choice to the user and he's this way able to have the environement the most suitable for him.
The only one problem appearing now for a couple of months is that Canonical is becoming a problem and split the community (read about MIR/Wayland polemic where they create another display server different of the one the others are working on. The main problem is that maybe AMD/nVidia will follow them).

To not quote something worse : I bought something like 10 months ago a Dell laptop for my sister preinstalled with Ubuntu (professional model). Never saw a Linux installation with that much proprietary drivers and so on (even a driver and its patch !) and it was a 11.10 while 12.10 was available or latest LTS 12.04. Did a format and tried to install something else. Fedora, Debian, earlier Ubuntu, Archlinux. Lots of drivers problems. Sad if you consider that
- The laptop was shipped with Ubuntu but with a very bad work from Dell with proprietary stuff
- My old Dell lapop from 2005 was running perfectly out-of-the-box, nothing to do. Same about my father's one from 2009. Really bad evolution from them.

Direct3D you mean? (It is still called that, right?) The massive difference here being that OpenGL only offers graphics options, whereas DX is a complex solution involving sound, input, well just about everything.

SDL 2. Many games (for example Witcher 3) anyway probably use lower level frameworks directly through their engines. For example on PS 4 it uses PSSL and other APIs, no DirectX there. So their engines are generic enough to allow plugging in multiple backends.

Lenovos tend to work with regular Linux out of the box, but I didn't buy laptops lately. I prefer custom built desktops, so Windows bundling issue is never a problem for me. But most users aren't assembling computers from separate parts, but buy them from vendors like Dell and Co.

Lenovos bought Thinkpad's IBM so I guess it can be good laptops for the professional ones, yeah.
I'll build my computer too for a desktop computer, but for laptop you don't really have the choice excepted by taking some models build on Clevo's frame. Not always the best solution and often more expansive (and you can't then upgrade it as easily as a desktop)

Last time I've checked SDL was designed to only handle 2D graphics. Not saying it's bad, programming I did for SDL was quite smooth actually, but it does seem limited.

SDL 2 handles 3D graphics just fine:

http://wiki.libsdl.org/FAQDevelopment#Does_SDL_support_3D_acceleration.3F

I'll have to look into that, if it's true, I'm a happy panda

Just note, it's not a 3D API, it's just an abstraction layer. You need to plug into OpenGL or Driect3D anyway. It makes life much easier anyway, when dealing with both.

It's not an anachronism. You know, community from each of these distros would be happy to package itself if something is just provided.
For example I like Archlinux but will never advice it to a beginner on Linux, as for Gentoo or some distros like theses ones. As I'll never use Fedora, Mint or others like this on a server. Every distro have specifities which could be useful for a category of peoples. Maybe too much of them exists, but a choice is a good thing.

About packaging, .bin works and some proprietary editors are able to use it (VMWare for example), so why not for games?
Moreover, I've to highlight the fact that the community can work on integration and packaging by itself. The best example is for HIB games on Archlinux : Archlinux provide what we call AUR (Archlinux User Repositories), repositories managed by users. So for every HIB games they provide incomplete package (without binary to avoid piracy) so you give to your package manager the file from HIB and then he do all the work alone as if it was a standard package coming from a standard repository.

Windows doesn't provide any choice (as in system itself). GOG and others can address Linux distros reasonably. This was all already discussed above, why are we repeating this?

It's provide choice in the sense that it provides a working open platform for third parties, so called ISVs.
In that respect windows is really great, the efforts taken to keep the platform working ("compatibility") are enormous.

Linux on the other hand provides nothing in that respect.

It's an anachronismus. Continous repackaging of software is a waste of ressources and still to slow & breaks to often. See this bug report: https://bugs.launchpad.net/ubuntu/+source/software-center/+bug/578045