Sell statistics

http://www.vgchartz.com/

doesn't include digital sales as that data isn't released.

If you want actual sales data, you're going to need to subscribe to NPD (and yes their methods for totalling sales has increasingly been under fire with the rise of digital sales). Vgchartz is doing estimates, and are not necessarily far off from the actual numbers, but it's only going to give you a ballpark figure.

Publishers ultimately are the only ones who know exactly how many units their games sold. Ubisoft would also let its employees know internally, on the intranet, what the actual numbers were. Others don't

wish there was a central, accurate source for this kind of information so that the game industry could be reduced to a massive pissing contest