Well, the first Playstation sold about 100 million units; the NES about 60 million. Of course they had longer to sell those units, this is offset by the lower population, lower cost, and a smaller market (less Chinese people were able to afford a NES or even Playstation 1). Even the Dreamcast sold about 9 million units, which wasn't enough to keep Sega afloat. To get to numbers of the same magnitude we need to get to the Sega CD with about 2.2 million units sold, and that's widely considered to be a huge failure.