This doesn't surprise me at all. As someone who nominated a portable game, Nintendo almost never gave their portable software much care compared to the console equivalents. Rarely did you get a situation like Link's Awakening that was clearly the next big entry rather than a side thing, more often it felt like their portable titles were handed off to smaller teams or outside developers.
The best Nintendo-developed DS games are probably like, Mario Kart, Tetris, and Rhythm Heaven. Not the usual suspects. You have to dig a little. Their portables were weird. Although just like a top ten SNES games list that has Panel de Pon, if someone listed these games I would think they had a more interesting perspective for sure.