Kart is the best all-ages game, in my opinion. It is fun to play solo, with family and friends in the same room, and with randoms online. Kids love it, adults love it, and I imagine cats and dogs do too.
If you have someone that likes puzzle solving, I recommend Captain Toad's treasure tracker. It is kid friendly. It is also a good workout for the ol' brain, but (for the most part) not frustratingly difficult. It is also cheaper than most of the other games, as it launched at $40.