DoomPPC is a Windows Mobile 5 port of Doom for Pocket PC. It uses GAPI library, so it should run in fullscreen on QVGA & VGA devices.
It was successfully tested on x51v, VGA HP iPAQ hx4700, QVGA HTC Wizard so far.
Usage and installation instructions can be found here.
Note: DoomPPC is donationware, so if you want to support its development, please consider making a donation.