being a quakeworld and quake2 player myself, what i'd personally love to see, are arm ports of the greatly enhanced clients used in the competative quake and quake2 communities, with opengl support. they have alot of bug fixes and functionality additions to the original clients, whilst staying faithfull to the original game.
sources of these windows/linux clients are ofcourse available as demanded by the gnu gpl. they shouldn't be too hard to port to arm linux/opengl es for a competent coder.
i would like to see ome symbian s60v3 games on n900. for example Worms World Party, Towers Trap, Dictator Defence and My Little Tank.
Board games are missing too on n900.
I would like to see World of Warcraft on the N900. If nobody does it then I will take care of it.
Edit: The thing is that I have already a LINUX client running (No, I don't mean a emulation of the original Windows binary). So it would basically need a port from X86 Linux to a ARMEL compatible version.
I have for example no idea if there exist a ARMEL version of Zthread?