i'm new here too. but this much has been said (many times) -- there IS a sega genesis/megadrive emulator in the works for GP32. How complete it is, I don't know. I recall it being said that the speed was pretty good and the sound wasn't there yet, and from the tone I suspect it's in a kind of 'limbo' (as in, no definite release date yet, but it certainly may be on the horizon)
my hopes are certainly up for that one. in the meantime, the PCE emu should more than fit the bill to tide you over! (again, haven't seen it wither - waiting for my GP32 to arrive in the mail - but from what i have seen it should be pretty satisfying!)