I spent a lot of time looking for a working GBA emulator for my Q, and came to the conclusion that the device just isn't powerful enough to really do it. A lot of the roms are too big to fit into system memory, and then the emulators that will load up are not landscape, and thus the screen is sideways.
There are some good SNES, NES, and Genisis emulators tho, and there is also a Game Boy Color emulator located on this site:
http://rainmakerrc.googlepages.com/home