I am 100% sure that this game would be a nice port on the dreamcast. It is based on SDL and -supports- OpenGL.
I don't know if I'll get this to work, but let's see if I can port it to Dreamcast.Aleph One is an Open Source 3D first-person shooter game, based on the game Marathon 2 by Bungie Software. It supports, but doesn't require, OpenGL for rendering. Aleph One was originally a Mac-only game, but there is now a cross-platform version based on the Simple DirectMedia Layer (SDL) library, that should in theory run on all systems supported by SDL (Linux, BeOS, Windows, Mac OS, Solaris, IRIX, *BSD, and others). Except for a few minor things, the port is complete and playable.