I don't think that we'll see the BoTW sequel until last least 2021, so there's time.
Most Nintendo-published games are good if you like those games: Zelda, Mario Odyssey, Smash, etc.
Get what you think you'll like and enjoy them :)
Here's a tip if you are ok with digital purchases:
If you get Nintendo Switch Online ($20/year, and you'll want it if you want to play Smash online), then you are able to buy Game Vouchers for $99.99 for a set of 2 until the end of July. They can be redeemed for most Nintendo-published content and will last for a year from date of purchase so you don't have to redeem them both at the time of purchase. Buying two $60 games this way will save you $20.
There also is a Mario Maker 2 bundle for $70 that includes 1 year of online ($60 otherwise) so that's another way to buy a game and get the online service at a discounted price.
While not available to redeem yet, they have announced that both versions of the new Pokémon game out in November, Luigi's Mansion out later this year, and others will be available to redeem via the vouchers.
When announced in May, I had planned on buying 2 sets of vouchers (4 games) and after E3 I've chosen to buy a third set of vouchers before the end of July. It's a good time to own a switch. :)