To give you an idea of my tastes, this is what I'm currently looking for on each system.
NES:
Splatterhouse
Haunted: Halloween 85 and 86
Starkeeper
Log jammers
Rollie
mega man II
Mario/Duck Hunt
Mario 2
Mario 3
Snes:
Super Mario World
Zelda link to the past
Final fight
Killer instinct
Joe and Mac
Gradius
Tmnt time
Donkey Kong country
Genesis:
Lion king
Aladdin
Golden axe
Sonic
Keep in mind that Im just now getting back into physical. Most of these can be found easily.
So Its a bit of a mix of nostalgia of the games I played when I was a kid and Homebrews. Are SNES homebrews a thing? I would assume so...