I feel like the key reason the PS4 is such a runaway success is because Sony lucked out hard.
And by that I mean, both of their competitors fell flat on their faces in the beginning of the generation. Xbox was $100 more with that stupid motion control peripheral no one wanted, and also had that always online/drm/used games shenanigans, betting more on being an "entertainment box" rather than a console. It didnt help that console looked like an oversized 80's vcr, and was less powerful than PS4 even though it was more expensive. And the Wii U.....yeah, its best we dont talk about that.
By the time Xbox and Nintendo got their act together (which took too, too long), it was too little too late. The PS4 snowball effect was too big to even attempt stopping.
I am not declaring if they do or dont derserve the success, I'm just saying PS4 would've topped out more in the 80-85 million range rather than the 120M+ its looking to be now, if Nintendo/Microsoft didnt have false starts.