Considering the Steam Deck can run just about every console game ever made up to PS2 gen (and a good amount made after), I'd say they have the Switch 2 beat on nostalgia.

Palworld for the win.

You can emulate almost any Nintendo game from before 2016 on a steamdeck. Just got to wait a few more years for the switch emulators to get efficient enough to run well on the steam deck!

I know I'm not the standard pokemon fan, but showdown still exists if you just like to battle. The in-game gameplay of pokemon has always been a little lackluster to me and I don't like VGC/doubles.

ROM hacks can be fun, and I have done some self imposed challenge runs. I can't see myself finishing any of the Prof oak challenges I did without emu speedup.

I still have my GBC with pokemon yellow and a flash cart with (almost, missing the new ones) every GB and GBC rom in existence on it that supports save states, and can emulate many switch games on the deck iirc if I were somehow nostalgic for those, and in fact can emulate basically any nintendo game from history I may be nostalgic for better than the switch, among other games nintendo didn't make.

Which one is the real nostalgia machine? (Hint: It's the Gameboy Color lol)

"Powerhouse"