The Wikipedia games lists tend to be quite inaccurate, best to use the actual companies stores if possible. Here from Nintendo
Nintendo DS - 1830
So yeah it's already surpassed WiiU and should surpass 3DS in just a couple of months.
I think a lot of this comes down to the Switch being easily their most friendly and appealing console for Indie Developers.
I dont thats most accurate also because I think thats only for US or Europe market, while you have plenty of games that are just for Japan or that were not released in Japan.