Well, there is Neverwinter Nights.
It is a 10 years old RPG from BioWare and it was ported to Linux. It is build on top of a graphics library that has already been ported to OpenGL ES.
It uses graphics that is very nice (for its age, at least) but can be run on 10-year-old graphics cards, as well.

I think after the proper adjustments it should be able to run on an N900 effortlessly.

Basically, all BioWare should do is just recompile their closed binaries for ARM, and they could create the BEST mobile gaming experience.