Handhelds...I always thought of them as consoles (personally).
And Akira has a point. Does an add-on device count? I was of the mind when I started this thread that true backwards compatibility was built in. It is likely therefore that his list is pretty much the definitive one.
Not to say Im not amused by hearing about these adaptors mind. I only ever knew about the Master System/Mega Drive one before this. I gather that these add-ons contained some or all the hardware from the lesser machine then? - using the advanced machine as a slave?
FromWithins anecdote about the SNES is also fascinating. Between that and the CD debacle, seems Nintendo's development of it wasnt straightforward. Hehe as a side note, I read on a website recently that apparently at one stage the big N considered selling the Famicom under the Atari brand! Is this true? Would be amusing if it was. Just imagine if it had happened eh?
I hadnt included computers as I thought it a lot more prevalent. Perhaps this was a misguided viewpoint though.