* Wii: 60 million software units total, 56% are third-party units or 33 million (Nov. '06 through June '08)
* Xbox 360: 35 million software units, 84% third-party or 29 million (Nov. '05 through June '07)
* PS3: 25 million software units, 82% third-party or 20 million (Nov. '06 through June '08)
That's the numbers. Well 3rd parties did spike because the summer was relatively slow but then Guitar Hero 3 came in and stormed, after November a lot of Wii versions of Multiplatform games took were top sellers.
And those numbers also prove that Nintendo can survive if 3rd party interests were low on the Wii while the 360 and PS3 relies on 3rd party sales to stay afloat. While Nintendo is a strong first party, 3rd parties on the Wii still has a big chunk of cumulative software sales so there is still a healthy balance between Nintendo vs 3rd party sales.
As of now the chart is a little inconclusive considering that the 360 sales chart depicted doesn't extend to June of 2008 since the point of the chart is to compare the first 20 months of each console's life cycle.