I would like a new entry for the Puzzle League series, preferably with the fairy characters from the original back. That game is overdue for a new release, since it is a fun Nintendo competitive puzzler. Heck, there's even a proposal for a indie game that takes after elements from Puzzle League! Puzzle League could even cross over with Puyo Puyo, featuring the Panel de Pon cast interacting with the Puyo cast.
For Dr. Mario, I hope that it switches things up by making the game more fast pace, because I feel that, compared to Tetris and Puyo Puyo, that game felt like the same game from before. Dr. Luigi is a good effort at switching things up, but it would be interesting to see how this game could be retooled to be a more suitable competitive puzzler.
In terms of series that I would like to see return, in a new form if need be, is Wario's Woods. It's a suitable type of game for Switch, with its head-to-head competitive potential. Perhaps it might even be retooled as a Captain Toad game, since Wario's just there to sell the game. After all, Captain Toad has enough elements to make that type of gameplay stand out.
Thanks for reading.