That's a toughie. Metroid is hyped, but almost exclusively for core gamers or Metroid fans. Hyrule Warriors is taking a massive IP like Zelda but using something more obscure like Dynasty Warriors. Hyrule Warriors to date as a whole has sold about 6 million so far. But Age of Calamity did sell about 4 million units.
Kirby has the broadest appeal. Kirby is a popular character, and his brand of cartoon racing is different enough from Mario Kart to be worth it to people.
Kirby wins. I think it's the game most likely to sell 5 million copies lifetime even if it's an uphill battle.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 122 million (was 105 million, then 115 million) Xbox Series X/S: 38 million (was 60 million, then 67 million, then 57 million. then 48 million. then 40 million)
Switch 2: 120 million (was 116 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
