Edge reports today that Left 4 Dead has created something of a salespocalypse at retail. Valve’s co-op zombie killfest has sold more than two and a half million units since launch for Xbox 360 and PC combined.

Keep in mind, this is only PC copies sold at brick & mortar retailers – the digitally distributed copies sold via the Steam portal don’t factor into that number, as Valve generally keeps those numbers somewhat obfuscated. However, when one takes into account that during Steam’s one weekend-long, 50% off sale in February, they supposedly moved more copies than they did during the initial launch period, that comes down to a hell of a lot of digital sales as well.

Those are  pretty impressive numbers any way you look at it – especially for a new IP only selling on two platforms (as Valve has a known distaste for PlayStation 3). What about you guys? Which version of L4D do you grab your peels on?