The Xbox One won't play Xbox 360 discs or XBLA games, and that doesn't really bother Microsoft Head of Interactive Entertainment Business Don Mattrick.

"If you're backwards compatible, you're really backwards," he told the Wall Street Journal.

Mattrick said only 5 percent of customers play games from previous generations on new consoles, so spending time to make that possible isn't worth it. Sony's PlayStation 4 isn't backward compatible from a hardware standpoint, but with cloud service Gaikai, it should offer a way to play games from the PS3 and older consoles.

It's been eight years since the previous generation transition, meaning players have had longer than ever to build up their libraries. That's a lot to lose - and even more so with the onset of downloadable games in the middle of this generation.