That Xenoblade 2 Expansion Story.
It's almost a whole new game, so many little changes... And the funny thing here is that it has a realistic shot of being better than the main game.
My bet with The_Liquid_Laser: I think the Switch won't surpass the PS2 as the best selling system of all time. If it does, I'll play a game of a list that The_Liquid_Laser will provide, I will have to play it for 50 hours or complete it, whatever comes first.