Some of this is subjective, just because I see people mentioning a bunch of games that I would consider spinoffs. Doesn't really matter though. Here are my picks:
Undertale
Adventure
H.E.R.O
Anteater
Dead Cells
Duck Hunt
Hogan's Alley
Astroboy: The Omega Factor
Celeste
Wargroove
Untitled Goose Game
That's mostly it. Even the games I could mention that are obscure to most would still be a sequel or spinoff (or later had a sequel or spinoff). The video game industry is full of them.
curl-6 bet me that PS5 + X|S sales would reach 56m before year end 2023 and he was right.
My Bet With curl-6
My Threads:
Master Thread, Game of the Year/Decade
Switch Will Be #1 All Time
Zelda Will Outsell Mario (Achieved)
How Much Will MH Rise sell?
My Bet With Metallox