If only openGL equal to or better than DX...
OpenGL is almost equal to DirectX.
The "almost" is not so much the API's fault, but the lack of support. Drivers and games are built, and optimized for DirectX. It will always be this way.
Gaming on Linux will never be a thing, not because Linux is not capable of becoming a viable gaming platform, but because partners like Nvidia and game publisher don't put effort into developing for a platform with 1% marketshare, especially when the other 90+% is DirectX ready.
(This is not counting, by the way, Xbox 360s--who to this day only use DirectX 10--of which there are more than Linux PCs and PS3s [who use OpenGL ES] combined.)
It's sad because the problem <I>is</I> easy to solve; it's just that the solution is hard to implement.
Shows how much you read the news, I think you will find NVidia, AMD, and Intel have all been working quite hard on the Linux OpenGL drivers, and as bench marks have proven, in some cases OpenGL has now surpassed Direct X. Steam coming to Linux WILL make it a viable gaming platform.
OpenGL and DirectX are set of APIs; for lack of a better analogous term, they are "languages." They can't be better than one another at this point; that's like saying a word said in English is better than a word said in Spanish. Both languages are mature enough for each to have respective advantages in certain areas, but for the most part they are equal.
The biggest advantage DirectX has over OpenGL is support. Nvidia is aiding Valve at optimizing their (beta) drivers for the upcoming Steam (beta) launch on Linux, and suddenly AMD and Intel are also "working hard"? Show me your source? As you'd know if you followed any news, Linus Torvalds himself has been quite
expressive towards Nvidia. Why? Because they have never cared about Linux. Steam is not Linux's savior, it's simply a program that acts as a conduit to a website that sells games (who happens to be owned by a company that makes their own); leaving the social aspects aside, that's all it does. Publishers are the key to all of this, not the salesman. Truth is, there's simply little to no ROI if you invest in Linux for gaming, and the sole reason for that is that other OEMs and game publishers are targeting 90+ % of the world first.
You could argue (as I've heard others argue) that since Linux is free, that 1% could potentially increase rapidly. True. But you have to ask yourself this: why would <I>anyone</I> do that? Assuming gaming on Linux becomes a thing, why would anyone dual-boot Ubuntu and Windows 7/8 for gaming? Drivers will always come last to Linux, per Nvidia's track record.
Games, even with publishers on board, will always come last to Linux. It's because of that, you know, 90% Windows market thing. Even when they do come, which OS you think will receive the updated drivers first? Linux? No.
But fine, leaving all that aside, assuming people get Linux for gaming, <I>why would anyone dual-boot Linux for gaming</I>? There are certainly not as many (quality) programs on Linux as there on Windows to justify the back-and-forth; or you mean to tell me people will simply dual-boot Linux to, sort of, join a cause? What happens when you need to get some work done, you'll go back to Windows? Why, then, would you do that if you can <I>already</I> wok and play on Windows? You see where I'm going?
There's simply no incentive.
I could show you many, many more logical reasons as to why gaming on Linux won't be a thing, or, perhaps, I could simply show you
this.