My desk is right near the office where the bigwigs meet, so I've seen the plans for Nintendo's E3, as well as playing some of the games myself as part of my job.
1) Smash Ultimate's next DLC character - Il Piantissimo. He's very agile, very nimble, very fun to play. Comes with a Noki Bay stage. Additionally, Brawl's Subspace Emissary mode is getting a remake as free content in Smash Ultimate.
2) Animal Crossing The Journey Home releasing in September. Like New Leaf you have your own town, but there's a big emphasis on going on holidays to different environments (Jungle, Desert, Snowy Mountain), meeting new folks and getting souvenirs and bugs and fish ready for the journey home to your own town.
3) Daemon X Machina release date mid-August. Will show a bit more footage, and detail the multiplayer mode.
4) Bayonetta 3 footage will be shown - includes two player co-op with one player as Jeane. Release date 2020.
5) Paper Mario HD Collection - Paper Mario, Thousand Year Door, and Super Paper Mario bundled together for Switch.
6) Mario Kart 9 announced. Very similar to MK8, but with loads of new tracks plus a track creator - very cool.
7) F Zero S - a brand new F-Zero game. Soft reboot of the series, but will have a fleshed out story mode as well as online MP.
8) Super Mario Odyssey 2 - not much info on it, but definitely in development and definitely very cool.
9) The Legend Of Zelda: The Winds Of Change. A follow up to Breath Of The Wild, with Wind Waker type setting (lots of islands in an open world sea). Will feature proper dungeons and classic items like hookshot and the red rod from LttP, so the game is somewhere between classic Zelda and BOTW in feel.
Anyway if you have any questions hit me up.