We had Megadrive, SNES and Master System. That's three.
I'm not sure I agree that the market can't support a variety of ecosystems. We already have PS3/Xbox/Wii, millions of people still playing PS2, iOS, Android (yes, they count, and outnumber the console platforms), and PC gaming. That's seven different platforms all doing pretty well.
That's two different generations of consoles: the Megadrive was competing against the SNES, while the Master System was Sega's previous generation console competing against the NES.
There wasn't a meaningfully successful third console in either of those generations, at least none that I recall me or my friends ever playing!
I think the poster is from Brazil, which had a very long and very interesting Master System history, which lasted well into the 16-bit era.
But you are correct, the SMS and the Famicom/NES were from the previous generation, which btw also has the same 2 ecosystem feature I've been talking about above. The Atari 7800 came in a distant 3rd to a distant 2nd dominated by the 1st place player.
I'm not sure I agree that the market can't support a variety of ecosystems. We already have PS3/Xbox/Wii, millions of people still playing PS2, iOS, Android (yes, they count, and outnumber the console platforms), and PC gaming. That's seven different platforms all doing pretty well.