for a retroshow there needs to be an emphasis on gameplay, which is what classic gaming did better. So while Phantasy Star and Utopia were outstanding innovative games, most people with 15-second attention spans wont be able to pick up and play those kinds of games.

for the SMS, you have to go with Alex Kidd in Miracle World

There really is no wrong answer for the NES, but go with something that you'll never see rereleased by the big N, Mike Tyson's Punchout would fit this bill (youll never see Mike Tyson in a Nintendo game ever again)

Gunstar Heroes for the Genesis

I think the SNES is the hardest system to choose a game for, i cant think of any pick-up-and-play type game that hasnt been rereleased for GBA

Tempest 2000 for Jaguar

Devil's Crush for TG16

Burgertime for Intellivision

Turbo for Coleco

Yar's Revenge for VCS