Probably Playstation. To me the question needs to be viewed backwards. If any one console hadn't happened, what would be different today? Playstation crushed Sega, took all of Nintendo's 3rd party support, and probably drew Microsoft into the market the following generation. Absent Sony, Nintendo and Sega were both faltering to an extent, it is possible the overall market would have declined, and maybe the market would not have reached the same mass market level.
NES is probably second.
Lifetime Sales Prediction - 6/29/2013
Wii U - 38 million
XBOX One - 88 million
Playstation 4 - 145 million