If they did it now, they should do a cross-generational thing. Like one challenge is an NES game, then an SNES game, then an N64 game, a Gamecube game, and a Wii game.
What games/goals would you choose for such a challenge? I'd say restrict it to only one game from a given series (preferably genre), so don't make it all three Smash games or anything.
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Black Turtle spilled my diet soda!