One thing that gamers love to do is argue with each other. About their favourite games, their favourite consoles and what is “best.” Usually that descends into what sells more – and even then people manage to find a lot of wiggle room to try and back up their console of choice. The NPD is an American only sales tracking system that, once a month, releases data about the top selling games and consoles of the month. In this generation, especially, people have a vested interest in the Playstation vs Xbox debate.
Worldwide there’s no contest – the Playstation has massively outsold the Xbox and it will probably stay that way for this generation. In America it’s slightly closer, and people often put raised stock in the US market since that’s where they live and most American’s don’t take notice of other regions, let alone know much about them.