look at the drop off. you're talking about double digit million sales, then down to 3 when third party shows up. the rare exception being DQ11 but sales of a majorly numeralized franchise exclusive on one platform should be expected to sell that well.
other platforms third party games are evenly distributed or even lead them.
That's not because third party number went up on other systems, it's because first party numbers went down.
Selling the same numbers but getting a bigger chunk of the pie chart doesn't change how well third parties are doing, especially since the platforms where third parties lead are more expensive to develop for.