I would love to see a new Mario + Luigi game done in 3D (or back to pixel graphics).
They have a lot more buttons on the Switch so the combat could be reinvented with relative ease.
An Ice Climbers, I think could work quite well.
They have two controllers built in with the Switch, and the Ice Climbers are well known to be a duo.
What you do is, have the game as a 2.5D puzzle platformer, where two players have to use their unique skills to climb, solve puzzles and ward off death.
I would also love to see a Captain Falcon game in the style of Yakuza.







