Except they don't have a userbase gap like that at all. You've been comparing console userbase to gaming capable PC machines.
The university I went to had thousands of capable machines in its labs and not one of them would have been used as a gaming machine. You can't just say 200 million machines = 200 million gamers.
If you take all the capable machines sold in business and education alone it must be more than half that number. Let alone enthusiasts that have no interst in gaming (like the folding lot on here), or people that buy a machine higher specced than they need.
My work PC is a quad core with 8gb ram and a graphics card that would play games fine, but it's not a gaming machine. I've got more than one machine at home that could play games. You could be counting some people three or four times in that number.
Its not my research, I did not pluck numbers out of the air. You concentrate on the 195m pcs sold, but ignore the separate gfx cards sold - are those sold to offices too? 80-100 million each year. Do office users update their Nvidia drivers (Nvidia has 180 million active users)?
All of these factors add up to 80-200m gaming pcs, while acknowledging that there are 1 billion PCs in the world overall.