Zanten already went over this. But the PS2 and PS4 are not comparable at all due to a multitude of factors.
And that is the point, PS4 is facing stiff competition in the Xbox One and still selling PS2 like numbers. Japan was much bigger back then, so if a console failed in Japan then it would not take off worldwide easily as seen with the Xbox. Instead we have Europe being a bigger market and guess what? The PS4 is dominating that market, and will continue to pull big numbers from that market. Which leads to yet again PS2 like sales.
We are in a generation where NPD and Mediacreate numbers do not tell the whole story or even the majority of it, it is Europe numbers and Rest of world numbers that matter. This puts a lot more emphasis on shipments.
For non holidays last FY Sony did 8.4m vs 6.4m for holidays. This year it is at 7m vs ~8m with Q4 to go as non holiday sales. Last year they pulled 2.4m and you better bet they will be up yoy as they have every Q this FY. Could be up to 3m making it ~10m vs ~8m. The vast majority of US sales are during the holidays, which de-emphasizes non holiday NPD months, expect 1m US and 2m rest of world for Q4.
So even though the situations are different for PS2 and PS4, it can easily be said that the PS4 is pulling PS2 like numbers.