LovePlus+, Ni No Kuni, and a few other Japanese titles were 512MB on the NDS
So there were a few exceptions, but really most DS games didn't even get as large as 256MB. In fact average DS file size was probably around 64MB. And frankly I'm not even sure the Switch will include the DS as a part of its Virtual Console. It made sense to include it on the Wii U given the way that system is set up, but I suppose if they released games that didn't require touch, or very few that did (where you might have to use the Switch portably, held vertically to divide the screen in half), they could make it work, I'm just not sure it would be the most ideal system for the DS to be a part of the VC.