I upgraded my handheld emulation setup and can now do up to Dreamcast (N64 and PSP too) on the go but I don't really know what to try out. There are a couple of DC games I've played the PS2 versions of like Resident Evil: Code Veronica and Dead Or Alive 2, which I used to test out how well Redream and Flycast worked but beyond that I'm not sure what to grab 
It would be fun to give Saturn emulation a shot as well but I'm not sure if it'll even be playable. From what I've read, in terms of emulation on Android devices, Saturn sits somewhere between the DC/N64/PSP tier and the Gamecube/PS2/3DS tier in hardware requirements. I figured I might as well ask for MD/Genesis recommendations to round out the Sega systems.
Dreamcast:
Seaman(must have working mic). Narrated by Leonard Nimoy, you take care of a Seaman, a fish/amphibian with a human face. You feed, educate, clean his tank. He'll even get sassy with you.
It's a very weird game, but definitely worth a try, if you can. It has its own spin on the "pet care simulator" style of things. I believe there was a sequel being planned, but if I remember right, it was cancelled over the poor reception towards the first game and the Dreamcast as a whole.