Citing data from sales tracking firm the NPD Group, Microsoft said that the Xbox 360's lifetime third party sales amounted to roughly 68M units, followed by the Wii at about 33.4M, and the PlayStation 3 at just under 20M. Third party titles appearing on the Xbox 360 sold 217,252 units on average, compared to an average of 132,517 on the Wii.

"No matter how you slice it, the Wii third party game story is not a pretty one," Microsoft interactive entertainment PR manager David Dennis told GamesIndustry.

In a GameDaily report last week, Nintendo said the Wii's third party titles were selling "better than our competitors," and provided a chart highlighting the Wii's software performance. Compiled with data from sales-tracking firm NPD, the chart appeared to show the Wii with a distinct lead over the PS3 and Xbox 360.

However, the data represented the Wii's total software sales, including games developed by in-house Nintendo studios--such as regular NPD chart-toppers Mario Kart Wii and Wii Play--in addition to those created by third party developers.

Though non-Nintendo developed Wii rarely appear among the NPD's list of a month's best-selling games, it is possible that was Nintendo referring to strong sales of specific third-party titles, or using some other metric.

The Wii edition of Vicarious Vision's Guitar Hero III: Legends of Rock, for example, has had consistently strong sales over the last few months, long after the Neversoft-developed Xbox 360 and PS3 versions dropped off the NPD's monthly lists.

TT Game's LEGO Indiana Jones ranks as another third party title that has sold better on Wii. Going by its first month on the marketplace, the Wii release of LEGO Indiana Jones outsold the six other editions, including the PS3 and Xbox 360 versions.