When I loaded Monster World IV, it gives me a message stating in effect "This game is only designed for Japanese Mega Drive systems" or something like that. In the standalone version of Genesis Plus GX, I'm able to switch console regions. How do I do it with Retroarch?
I don't get that at all right now on the libretro version of Genesis Plus GX (PS3) - and that really shouldn't differ in anyway from the Wii version. Monster World 4 just works. Are you using the no-intro romsets?
Anyway, I'll be sure to check it out before I do the release.