Don't do a Zodiac, SNES gaming is too slow and Genesis is iffy at best. I got an Axim X50v and it works pretty good. SNES runs almost full spped with 16bit sound. Genesis does not. TurboGrafix16 runs full w/sound. I can even play PS1 games on it, not full speed, but some games do run almost full with sound! Like Einhander and some others.

MegamameCE on an X50v is where it is really at as I play some of my most fav arcade games on it. Like:
Asteriods, Berzerk, Congo Bongo, Centipede, Donkey Kong1,JR, and 3, Dig-Dug, Frogger, Galaga, Joust, Defender, Jungle Hunt/King, Kangaroo, Moon Patrol, Pacman/Ms pacman/Super Pacman, Q*bert, Star Wars, Tempest, Zaxxon...all good stuff. All run nearly full speed with sound (sound varies by game).

Controls are good and responsive. The VGA screen is awesome. Price is good. Stay with a PDA. No handheld has got the speed yet unless someone cracks the Nintendo DS or Sony PSP.