Saying that the New Super Mario Bros series is selling poor... comparing the sales of platforms that have a very big difference in the install base just doesn´t make much sense.
Let´s compare the attach rate to see how poor they´re performing actually
Wii: 100 million - NSMBWii 27,5 million (27,5 %)
WiiU: 3,9 million - NSMBU 2,11 million ( 54 % )
DS; 153 million - NSMB 2 29,5 million (19,3 %)
3DS: 35 million - NSMB 2 6,41 million retail only (18,31 %)
All games have attach rates above respectable 18 %. Something that even GTA V doesn´t have.
And... I wouldn´t call Super Mario Bros series as "casual". This is a series of games that have been around since the 80´s, way before something like "casual gaming" even existed. A big chunck of Mario games audience is not definetely "casual"
We should take these series of examples of how casual gaming are really losting appeal, since they were launched after the born of this cathegory of games:
Just Dance (2014 is really selling poor)
Rock Band
Wii Party/Fit
Brain Age
Dance Central
Kinect Sports
Nintendogs (still one of the best-seller games on the 3Ds, though)
