I think the X11 ROM is the best. I use snes9x, dosbox, gnuboy, stella, and x64. (basiliskII works but MAC OS 7 has problems dealing with taps: it thinks every tap is a mouse drag from the last tap. very annoying.)
I got stella(atari 2600) and gnuboy from the debian-ARM distribution.
Many of the emulators mentioned above use SDL, which is horrible in qtopia but works just fine under X11. Under qtopia, I always ended up having to reset my Z to get out of the emulators. Also, there are a lot of qtopia SDL libraries out there and I could never figure out which was best for which emulator.
