Just the Megadrive for now.
Over the weekend Sega announced that a range of Sega Ages titles would be coming to the Switch, all of them from the Megadrive.
Only Sonic the Hedgehog, Thunder Force IV and Phantasy Star were confirmed to start, but later in the day Alex Kidd and arcade title Gain Ground were confirmed as well. Alex Kidd was chosen because of its great performance on the Virtual Console, especially in Europe.
When asked about other systems, Sega said that if Sega Ages does well past the initial 15 games that will be offered, Dreamcast and Saturn games could also make it in the future.
What Dreamcast and Saturn games would you like to see on the Switch?
Source: Game Watch, Resetera
It's Black, Back Again.
If these aren't the coolest graphics...
Loco Motive, MySims: Cozy Bundle, Stray, Nine Souls, Servonauts.