Interesting comparisons, but hardly surprising. Sega was already dead in 2002 and the PS2 had for only competitors the gamecube and the 1st xbox which couldn't have a big impact on the market...
Also, let's not forget that PS2 had something that PS4 hasn't, the help of the huge success that was the DVD at the time. So many people bought a PS2 as a cheap DVD player !
I think the PS4 numbers are still quite remarquable tbh, even compared to 2008 and the PS3/Wii/360 era. Today the competition is crazy, with Steam, smartphones and tablets, Microsoft and Nintendo also still around (although less strong) people have so many choices and can play literally everywhere.