I agree that the DS has been forming the massive succes it is now largely thanks to Nintendo and Nintendo alone.
Seriously, every aspect (not just the games/system sellers) came from Nintendo. 3rd party's where seriously jumping on starting the end of 2006/beginning 2007 when a lot of good titles started hitting the shelves (and I mean Japanese third party's, cause western devs are to this day almost no where to be found sadly).
3rd party's are sustaining DS incredible succes, they have not caused it. Even Square Enix, whose impact is far beyond every other third party only "recently" announced the three Dragon Quest remakes and a while before that DQ IX -- the most important 3rd party titles the DS has by far --, obviously when the DS was already doing seriously crazy numbers every fucking week. Just saying, Nintendo sure handled the DS brilliantly and they should be getting props for that.
Now it's 3rd party's time to shine though, and they seem eager to do just that.
I searched in the last couple of pages but is the Galaxy 250k number confirmed? Not very good imo, even though it's not much lower than Sunshine's and will most likely have very good legs. How was the marketing for the title in Japan?