I think ARMS is the next big thing for Nintendo.
The game is REALLY good. It also demonstrates the advancement of motion control technology, this is the massive leap that was required with Wii Motion + or whatever new controllers they should have had with the Wii U.
It's a lot more than just Wii Boxing, there's a lot more movement involved, WAY more moves, weapons, etc... It's probably more like Smash Brothers, but with the thrill and flash of Mario Kart, and unlike Mario Kart - it is completely fresh.
My one complaint is that I wish there was a mode that was similar to Smash, in that you rack up as many kills or damage as possible in the time period, rather than just simply being the last one left in a 3 or 4 player match. I got the hang of the three player matches though, just dodge like crazy and try to manuever the other two into attacking each other. No plan is perfect, but it plays to stay active and take out the stronger character, or just avoid the fight as much as possible. Anyway, the avoidance strategy would be invalidated if it tracked damage delt rather than being the last one left.
ARMS is the most fun game on Switch right now, it surpasses Mario Kart in its base game.