I'm going to make a recommendation for pretty much all the metroidvanias, the deck was practically built for them. The Castlevania Advance collection has three great old games, including Aria of Sorrow, which was the progenitor of Bloodstained (which might honestly have a little too much going on - if you feel like you'd enjoy a simplified version of that, Aria is your game.)

But also do remember to pick up Hollow Knight. And Blasphemous. And if you're emulating, Metroid fusion, Zero Mission, Metroid prime even, if you feel like frigging around with the GC emus.

Also, Soulslike games play particularly well on deck. I can get a pretty stable 30 out of Elden Ring, I'm sure the older titles work pretty well too.