Using known brand lessen the risk, yes.So does Nintendo keep making games with the same mascot character because they always sell, or are they the only games available therefore it's all the console/handheld owners can buy?
However in case if Mario he is more a "face that rappresent Nintendo quality" than a character otherwise he could not have survived the eighties or nineties unscatched.
Mario and co are a coat of paint over the gameplay Nintendo create (if Mario characters fits into the universe of the game otherwise they create new characters like with Splatoon).
Nintendo games of course aren t the only ones a owner can buy on their platforms (even on WiiU) however they are the most likely to be bought.