Really I expect every first party game to become the best selling ever at this point: Donkey Kong Country, Metroid Prime 4, Smash Bros... I expect them to all sell like crazy. I don't know why, but the market is on fire for Nintendo first party.
I sure hope you don't mean the port of Tropical Freeze, cos no way in hell is that outselling the original Donkey Kong Country's 9.3 million.
Bet with Liquidlaser: I say PS5 and Xbox Series will sell more than 56 million combined by the end of 2023. (And over 130 million lifetime)