Based upon March sales the Nintendo Switch only had one million+-selling game - The Legend of Zelda: Breath of the Wild. Yet with 2.74 consoles shipped some other titles also clocked up reasonable numbers, something Nintendo President Tatsumi Kimishima highlighted in his recent investor briefing.
First of all there's 1-2-Switch, which was the 'other' major first-party retail release in March. It was stated that it's "on track to ship one million units very soon"; this certainly aligns with the sight of the title hanging on in software charts in different territories. Considering the userbase for the console so far, an attach rate of a third or more isn't at all bad.
We also have a better idea of why Konami is evidently happy to work on updates, improvements and free DLC for Super Bomberman R; Nintendo's reported that it shipped over 500,000 copies of the game. That doesn't mean they've all been sold on to gamers, but evidently retailers have wanted to have it on their shelves and decent numbers are picking it up.
Finally, Snipperclips - Cut it out, together! has been a success story on the eShop; that's unsurprising as it was published by Nintendo. It's been downloaded over 350,000 times, and Nintendo doesn't suggest it's counting demo downloads in that number.
There were various other high profile March releases, especially on the eShop, but these numbers do prove that Switch owners were indeed looking for additional games to play beyond Breath of the Wild.