I don't think that family friendly and casual titles are losing their appeal on Nintendo platforms, only that certain series have lost a bit of appeal, and this is supported by your data.
The NSMB Series - when it debuted it was an event. I can remember my regret having purchased a PSP when I saw people at work playing NSMB on DS. 2D Mario platformers had been dormant for so long, the pent up demand was crazy. Now they've done it 4 times without offering too much that's new. It's like Brett Favre's 4th comeback or Michael Jordan joining the Wizzards. Not big news anymore.
Brain Training - This is a series that has been hugely impacted by smartphones. Also, edutainment isn't really all that fun.
MarioKart and Animal Crossing are loved by casuals and continue to thrive. I think Wii U is ripe for a good casual title that uses the touch screen, but it needs to be something creative. I'm curious to see if the Wii-Series still has appeal.