Bolstered by sales in Japan, Sony has announced that the PlayStation 4 has sold six million units worldwide. Perhaps more importantly, Sony also says that 13.7 million PS4 games have been sold -- an attach rate of almost 2.3 games per console -- with Killzone: Shadow Fall leading the pack with 2.1 million units sold. The exact number of Xbox Ones sold is unknown, but it's probably just under four million.