Rules: just pick 1 and explain why.
I’ve been playing since the NES and despite being from a low income family I had the luck of being able to play and own many consoles over the 3 decades of my life, plus some pc.
If you ask me right now? Resident Evil 4 (2005).
A before and after in gaming, to this day still extremely fun to play even for casuals but 20 years ago it was THE masterpiece. And everyone took notice of it, everyone played it, even players that didn’t cared about resident evil. The gameplay was so good that it got photocopied by everyone right after in the action genre.
Arguably the last big innovator in videogames minus Minecraft and… PUBG (Fortnite did it better I know).
Try to NOT pick your favourite game, that’s a different thing.
My answer is SNAKE BYTE!
Just TWO keys, none of that FOUR KEY nonsense from other snake games.
It doesn’t matter how old I get, I will always go back to Snake Byte and spend hours playing it when I do.
I was thinking before reading the comments and nothing came close to Tetris in my mind. This is probably the true 2nd place