So on Nintendo's website they have a list of licensees and associated websites who are allowed to legally create products for Nintendo ranging from Toys, Apparel, etc. I went to each site that was still active and looked at all their product and found out which one was the best sellers and boy the results were quite interesting.
In clothes, Zelda and classic Nintendo (SNES controller shirts etc) are king in being bought by men. In boy sizes however Splatoon does really really really really well. Junior sizes bestselling Nintendo IP seem to be Animal Crossing with Toom Nook, Resseti, and Redd the Fox Tops and Tanks. Women tended to buy the Star from Mario and Princess peach gear. Girls sizes sell a lot of Yoshi, DK, Mario and friends gear. There appeared to be little to no Kirby gear however people did buy Star Fox and Pikmin shirts.
In toys, Kirby and Pokemon reign supreme based on wholesale. However individually using ToyRUs, Walmart, Target as the General public for what toys sell well in regards to Nintendo, Animal Crossing by far blew out all the competition. This was followed by Pokemon, Mario Friends, and Kirby. Zelda Splatoon and Pikmin toys were present. ToyRUs bestsellers is creating a very different picture at the current moment with Animal Crossing 100% leading the way. However down below is 2015's number and it strongly demonstrates the distinct tastes each region has in regards to Nintendo.
These were the best selling amiiboos in 2014
And these were the most sought after and always sold out figures in 2014
In art books and collectible figurines, its also an even spread of Zelda, Metroid and some Kirby. Based on the licensed Nintendo figurines, Zelda and Metroid have a much larger selection followed by Kirby and then Mario and DK figures also present is present.