While Microsoft is the company that's just been touting global console sales figures, it may well be Nintendo's Wii that has the largest installed base for a new generation console.
17.7 million Xbox 360s have been sold worldwide since launch, according to Microsoft. Using the figures currently available and a bit of educated guesswork, it's not unreasonable to suggest that the Wii has topped that figure - despite having been on sale for a year less than the 360.
According to Reuters news agency, by the end of September last year the 360 had sold 13.4 million units. The Wii, meanwhile, was a smidgeon behind with 13.2 million units sold. That means that to have exceeded the 360's sales, more than 4.5 million Wiis needed to have been sold since then, while 4.3 million 360s have been sold in that period.