According to NPD third-party software figures, Microsoft's system has sold 67,929,999 units, followed by the Wii at 33,394,311 units and the PlayStation 3 at 19,976,325. Looking at sales occurring since the launch of the Wii, the Xbox 360 has managed 54,065,728 units (compared to Wii's 33,394,211), though it obviously benefited from having a larger install base to feed off at the time.
This particular third-party tussle has been going on since last week, when the NPD delved into sales numbers and revealed the Wii to be ahead when compared to its competitors' initial 19 months. It's all a matter of perspective, you see, albeit one that publishers (releasing games for the market as it exists right now) might not necessarily adopt. Still, with the hardware battle being won by Wii, it isn't surprising to see Microsoft putting up a fight on a more even battleground.