In the short term, it was a phenomenal strategy.
In the long term ... it's not helping them. They can't compete with Apple/Google for casuals anymore than they can compete head on with Sony/MS for "hardcore" players. Probably less actually.
A "hardcore" player would probably give the Wii U a look at the right price/games and some good marketing, casuals today are so far gone that they won't touch Nintendo's $40/$60 per game model. Mario is nice, but next to free/$1 casual play games and much "cooler" fashion centric smartphone devices ... Nintendo can't compete with what the casual player expects today.
I don't think there's much Nintendo could've done with the Wii U/3DS to attract large legions of casuals this generation out unless they were willing to make smartphones basically and charge $1/game. There's just no reasoning with this audience any more, they got a taste of that and now won't accept anything different and the whole appeal of smart devices is that they replace the need for multiple old devices, which means tough sh*t for all console makers wanting casuals (Kinect in XBox One was a liability as a result too) and handhelds are in huge trouble.
Whereas on the flip side, if they Nintendo taken advantage of their year headstart and made a decently powerful next-gen console with some good games, they honestly could be sitting fairly well off right now. They wouldn't beat Sony's PS4, probably not in the long term, but they likely could've beat the XBox One in this situation and finished with a decent no.2 standing this gen if they had executed properly.
Instead they compromised and made a "sort of" casual machine with the Wii U -- underpowered, gimmicky, lots of mini-games and casual Mario fare early on.
