"At least with the Genesis you could get a converter and run Master System games (I've done it, it works). "
You can thank the onboard Z-80 for that---Genesis used it for Genesis games as a sound processor, whereas it was the main cpu in the older SMS. In a sense, thats what Nintendo tried to do with the SNES, put in a backwards compatible 16-bit chip, they just didnt pull it off as well as Sega did. Might have made more sense to put a 68000 in there, like you said, and put a 6502 alongside it, similar to how Sega did their backwards compatibility. One think I always remember SNES devs complaining about was what a dog the 6502-native compatible WDC 65c816 was compared to the Genesis' 68K. Which was a shame, because everything else about the SNES hardware was far more capable than Genesis.
Again, probably came down to a matter of cost.
You can thank the onboard Z-80 for that---Genesis used it for Genesis games as a sound processor, whereas it was the main cpu in the older SMS. In a sense, thats what Nintendo tried to do with the SNES, put in a backwards compatible 16-bit chip, they just didnt pull it off as well as Sega did. Might have made more sense to put a 68000 in there, like you said, and put a 6502 alongside it, similar to how Sega did their backwards compatibility. One think I always remember SNES devs complaining about was what a dog the 6502-native compatible WDC 65c816 was compared to the Genesis' 68K. Which was a shame, because everything else about the SNES hardware was far more capable than Genesis.
Again, probably came down to a matter of cost.