'When designing your OpenGL ES application, the first question you must answer is whether your application will support OpenGL ES 1.1, OpenGL ES 2.0, or both. That is, they'll allow apps that are only compatible with the 3G S because they're written to take advantage of OpenGL ES 2.0 and don't offer a 1.1 fallback:

The App Store has already splintered a bit with certain applications being unavailable to iPod Touch users (dialers, for example), but language in Apple's iPhone SDK documentation leads us to believe that the company eventually intends to begin allowing it to splinter even among iPhone models, maybe as soon as the 3G S is released. A 2.0-only app can't simply run on a 1.1-only device and not look as good - it won't work at all. Here's the problem, though: because OpenGL ES 1.1 and 2.0 are completely incompatible with each other, apps need to be written to support both if they're going to be maximally compatible. What does this mean to you? OpenGL ES is the lightweight version of OpenGL, a powerful library of real-time 3D rendering APIs many modern phones and other handheld devices support the older 1.1 specification, but 2.0 is less common - it kicks things up a notch by supporting more complex textures and shading operations, which basically means games written to support it look more badass. Turns out, though, that the graphics processor in the 3G S - the PowerVR SGX - supports hardware acceleration of both OpenGL ES 1.1 and 2.0 while the more pedestrian PowerVR MBX found in the iPhone 3G supports 1.1 alone. When we were breaking down the meaty differences between the old-school 3G and the 3G S yesterday, we made an assumption about support for OpenGL ES 2.0 3D graphics APIs in the original iPhone 3G based on the fact that it had been available in the iPhone OS 3.0 SDK for several betas.

Opengl es 2.0 apps