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.
Vigilante 8: 2nd Offense for the Dreamcast is a fun vehicular combat game to mess around in. I always found the mechanics to be more satisfying than other games.
I have played Vigilante 8: 2nd Offense... but on the PS1. Maybe I should look into PS1 games that I like that got DC ports, though I will say that the Dreamcast having only 2 shoulder buttons is annoying when you're used to a game being able to use more, like with DOA2 where you have two less options for binding button combos