Cat whom just received their Playdate
Okay, one immediate game recommendation:
Zero Zero Perfect Stop
https://play.date/games/zero-zero/
It is a japanese train driving simulator (as-in, a simulator for driving a japanese train through japan), with the crank serving as a combined break and accelerator lever.
Really intuitive, and a pretty good way to play that kind of game on the go (though I cannot make a direct comparsion with Densha De Go, as I don't have any direct experience with that franchise).
Zero Zero: Perfect Stop for Playdate

Welcome aboard the Fuji Express!

Oh, and naturally, someone has ported DOOM to it. https://devforum.play.date/t/doom-on-playdate/852/57 #ItRunsDoom
Doom on Playdate

Hello! I've compiled code from GitHub - spazzylemons/playdoom: Doom port to Playdate based on Chocolate Doom repository with SDK 2.4.2 I've modified only the Makefile. Here's the version for device. It works smoothly on my Playdate with 2.4.2 firmware. Makefile.zip (624 Bytes) PlayDoom.pdx.zip (3.1 MB) Don't forget to place doom2.wad in the game's data folder (PLAYDATE/Data/me.spazzylemons.PlayDoom) or the game will not run.

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