The racist comment is quite weird.
But hes not adding up different generations, they are all different variants of the same hardware.
As for NES, its estimated that it had ~80% marketshare which is similar to the ~75% PS/PS2 had.
Oops, you're right, I was thinking Master System instead of Mega Drive. Damn Sega for being confusing.
80% market share is enough for me to think of something as a near monopoly, especially with it being even higher in North America. Still, I don't really care that much--if he wants to get offended over "near monopoly" then I can change it to "near near monopoly" or even "near near near monopoly." It's a ridiculous thing to get bent out of shape over.
The point is, it's an interesting subject that would make a good documentary.