I cant 100% recall Sonic on the master system but then again I was very young back then 😆. I do remember Alex Kidd and wasn't there another built in game I cant remember what it was but i'm sure you had 2 built in games with it I just cant quite remember.

Also the Mega Drive I remember i got it for Christmas and it came with Sonic and I think it was a 3 game cartridge Golden Axe, Shnobi? or something like that, and something else i cant remember. Golden Axe was another classic lol