As I've mentioned before I'much of a mobile or smartphone gamer, so the only game I'd possibly play would be Mario Kart. The only games that I think work well on the smaller screens is the racing games, but having said that, I can see even Mario Kart being a struggle for some people due to the speed and actions of the gameplay involved.
In all honesty, I'm not sure what extra exposure Nintendo would get from releasing their games on the mobile platform, and while I suppose any bit of exposure helps, I'm not really sure it will be worth the effort involved to be honest, but I'm sure Nintendo know more about that than me.