So besides mobile consoles, PS2 is the indisputable king of home consoles from gen to next gen.
There is something amazing too from those numbers. PS3 almost stop selling after PS4 was out.
But PS1 sold a lot more reaching more than 100 million units.
Acording to that info PS3 sold like 7 Million more after PS4, but PS1 sold 30 Million more!
And with 94 Million units shipped, PS4 can sell very close if not surpassing PS2 from gen to gen.