I'm 40+ and I lived through those times. My only complaint in all these calculations is not the number of people, frankly speaking it doesn't matter at all. Since consoles were always bought in regions of the world where the population did not change so significantly, the main population growth is shown by countries in Africa, Asia (India). In the rest of the world we have long been in a state of Birth Rate equal to Death Rate and this is in the best case, usually Birth Rate is significantly lower than Death Rate.
The problem with all these calculations is consumer power then and now. I still remember how I was given my first NES for my birthday, and I remember that my father put it off for a long time and I don’t remember the exact cost of the console, but something around $170 (that’s about $500 now, taking inflation into account) was a lot of money at that time, and the Mario cartridge that was included was my only cartridge for a very long time, and I don’t remember the exact price of the cartridges, but they were around $50 each and $55 for Nintendo hits (Mario 3). Most of the games that I had and played, I either swapped with friends or rented, the question of buying games in the family was never even raised, only as a gift for very big holidays. To say that a NES in the 90s was a great luxury is to say nothing, and not everyone could afford it. That's why NES sales are so impressive.
It's not that consumer power has grown very much now, but the market has become much more flexible, and a much larger percentage of people are buying consoles now. Nowadays, buying a console is a fairly common event, they are not that difficult to buy. Games are expensive at first, but their price drops rapidly, and then drops to ridiculous levels due to endless sales.
