Correct me if I'm wrong (written lots of OpenGL and DirectX over the years, but never worked on a console), but doesn't the PS3 use PSGL, an OpenGL offshoot that's not directly compatible with other OpenGL implementations?

Which is to say, porting effort to PS3 does not also give you a PC/Mac OpenGL port.

This is the big problem I see - UE and idTech both support OpenGL, though in reality only UE has any significant licensee base to speak of. There is, however, an awful lot of home-brewing even at the AAA-levels: EA's gone and thrown a lot of weight behind the Frostbite engine, Ubisoft seems quite fond of their Anvil engine (Assassin's Creed + more), and the big massive CoD franchise runs a proprietary engine too.

An OpenGL-only platform might automagically include all UE and idTech licensed games, but that's hardly an impressive snapshot of the gaming industry, particularly the core gaming demographic (as compared to say, the mobile gaming demographic, where OpenGL already reigns supreme). This hypothetical platform won't just leave the vast majority of Steam's existing titles in the cold, but will also have the unenviable task of forcing many devs to provide cross-platform support where none currently exists.

Valve is a juggernaut in the industry - but even that's a very, very tall order. There's certainly a renaissance of interest in OpenGL thanks to the mobile gaming side of things, but I'm extremely skeptical of claims that any player, even someone the stature of Valve, can get a majority of existing Steam devs to sign up to support OpenGL.

So, the PS3 does support PSGL, but that's not actually what you are thinking of. PSGL is a GLES variant (Not exactally, iirc, GLES 2.0 wasn't out then, and GLES 1.0 didn't have the required shader support). If you wrote your game to run using PSGL, you were actually doing pretty good for a full OpenGL Port.

Now, you are actually in fact thinking of LibGCM, which has very few similarities to OpenGL, is much lower level, simpler, and is in fact, the library that most PS3 developers do end up using.

Do however keep in mind, that any major game that runs on Mobile, OS X, or Linux, has pretty much API compatible library usage with OpenGL.

Then while the PS3 doesn't give you OpenGL, any cross platform game that runs on both PS3 and another system generally has a graphics system abstracted enough to make porting to an OpenGL system while not trivial, a rather well contained and limited amount of work. Surely enough to make it warranted to port to whatever graphics API Valve chooses to use, should it be a successful console.

And frankly the Microsoft monopoly on rendering API's. These days modern OpenGL is close enough, to not really matter. Having nearly feature parity, and these days all the fancy stuff happens in shaders anyways, the API just doesn't matter as much as the platform lock-in these days.

Yes, the steam console doesn't automatically get access to the entire library, but keep in mind, Steam on the mac has been hugely successful, and it had a very limited selection of games to begin with. You say that valve can't get a majority of existing devs to sign-up to support OpenGL, frankly they don't have to, rather they have to get just enough Steam devs to do such, and that's something history has shown that they do in fact have influence over.

Frostbite and Anvil run on DirectX and OpenGL-esq systems. IW engine even has games out on Wii. I kind of suspect that all the major engines out there have pretty decent cross-platform support these days. The publishers don't like to be locked into any one console unless they are getting an exclusivity kick-back from Sony, Nintendo or Microsoft.

It might require Valve to get people to recompile their games and tweak some stuff, but like you say, Valve are a juggernaut.

I think you're mistaken, Frostbite doesn't run on any OpenGL-esque systems.

The PS3 is OpenGL based. Specifically it's OpenGL ES with some extra proprietary Sony stuff. The important point is that the engine is not directly tied to any low-level rendering API and clearly has enough abstraction to be ported to multiple platforms with a reasonably low cost of development.

Your first comment isn't entirely accurate. While the PS3 does support PSGS, which is the library you are referring to, engines like FrostBite use the LibGCM interface, which has very little similarity to OpenGL.

The PS3 is not OpenGL based, it provides an optional OpenGL-like layer should titles want to use it but rarely do any these days use it. Frostbite pokes the GPU FIFO directly using the libgcm.

RAGE uses OpenGL on Windows too, and it cost them because the AMD OpenGL drivers were broken when RAGE was released, causing major graphical glitches with AMD cards.

Again, DirectX does have advantages. But they are seeming less and less important in comparison to the platform support these days.