If I'm not mistaken, the NES ended the 3rd generation with about 90% marketshare...was there any other previous system that had over 85% marketshare?

Who was it competing with?

SEGA Master System.

Yup, just looked it up. No wonder the NES crushed it then.

I'm not sure it is the closest it can get, but it sure was the closest any system has been thus far!

Yes, it's the closest thing to a monopoly. It was also the most impressive display of the abuse of market power.

Yes, NES dominance makes the PS2 look bad (which is saying something).

yes it was, it controlled everything!!

Atari 7800 and Sega Master System were the compeittion.

The NES had an 82% market share. The next closest home console was the PS2 with a 73% share.

Exactly...