It all depends on the game.
SDL 1.2 does not know OpenGL ES, that's why OpenGL ES on SDL 1.2 is impossible. (although there are special version that gave GLES support, but that were never official).
SDL 2.0 does know a lot more backend, OpenGL, OpenGL ES 1.1, OpenGL ES 2.0, Wayland, Mir, Windows Phone, etc.
This makes SDL 2 more universal (what's the goal of SDL 2 anyway).
Still you can still program in OpenGL and just use SDL 2 to initialize the rendering window. Which apparently seems to be the easiest way for developers, since many projects work like this.
But that means, it only runs on OpenGL even if SDL 2 is compiled for OpenGL ES and you only have a OpenGL ES system.
So this sucks and often is a show stopper.
Anyway.. With this projects it was relatively easy. Since it was originally made for iPhones/iPad and for that already written for OpenGL ES. And someone just ported it to Linux using SDL 1.2 and OpenGL.
It was rather easy to move to SDL2 for this project, I just had to fix some includes, rewrite the SDL_Init, which allowed me to scale the game from originally fixed 320x480 to Desktop resolution
But not every project is that easy.