I do have a game gear in my closet somewhere but I have that problem where the sound stops working and the screen is all fucked up and hard to see - still way better than a stadia tho..
Gba SP would be better candidate imo. Cause without modding you have a shit load of games from a few generations. Including Sonic, Mario, Crash Bandicoot,& Spyro. Great battery life, rechargeable. Tons of peripherals too make the experience even better.