I agree with regards to the PS1 and 3, it's not true for PS2. It was quite hard to still get a PS2 after four months off its European launch. You could get one, but it wasn't readily available yet at that point. It had a huge demand. You can see from the shipped numbers that they were flying off the shelves in their third fiscal year. The production numbers had to ramp up to really high. I'm only fixated on using these shipped numbers as a point to your argument not the argument itself.
Fair enough. I don't think you can just extend the period out any further, though, without the comparison becoming even less valid. Right now the PS4 is as expensive as it's likely to be, has the smallest software library it will ever have and has the smallest feature set it ever will. Those other consoles were already enjoying the numerous benefits of additional time on the market and those benefits made them increasingly appealing products. I'm trying to compare demand, so even if what I put froward was an imperfect comparison, I'd argue that it only gets more imperfect with added time on the market.