PS2 did 5.51m in 2005. That looks very close to what PS4 will do this year. Hard to say which will come out on top if you compare this year's PS4 to 2005 PS2.
Ya this will be a fun comparison, if I can find the individual months for PS2 in 2005 I'll make a thread for that battle too.
When the herd loses its way, the shepard must kill the bull that leads them astray.