RetroArch

Okay, sure, this one’s technically not a game on its own, but it’s kinda hard to ignore how awesome it is to be able to emulate all kinds of retro consoles with one of the best emulator suites out there—and it runs super well on the Deck.
With a wide selection of emulation cores that simulate everything from Atari 2600 to Sega Saturn, Dreamcast, and PSP, RetroArch transforms the Deck into a time machine. I’ve been able to revisit and finally finish Super Mario Bros., as well as annoy the hell out of people at family gatherings by playing Gex on the couch.