The boys at WebOS Internals have been busy lately porting SDL (Simple DirectMedia Layer) games over the Pre. Currently there are 4 titles available via Preware (or your favorite homebrew installer) with a 5th already announced.
The current game list is:
Doom - Classic FPS
http://www.precentral.net/hardware-a...d-yes-its-true
Quake - Another Classic FPS
http://www.precentral.net/playable-q...ebos-internals
Super Tux - Super Mario style game utilizing the accelerometer.
TetriCrisis - Tetris Clone
Classic Invaders - Space Invaders utilizing the accelerometer.
And coming soon: ScummVM
http://www.precentral.net/shape-game...-scummvm-webos
ScummVM is a program that allows you to play old Lucas Arts games like Monkey Island, The Dig, Full Throttle, Loom, Maniac Mansion, Broken Sword, Etc.
Not sure what's next but there are a number of emulators for NES and the like out there that are SDL compatible.