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.
Ocarina of time. All Zelda games since are to some degree compared to it in terms of how successful it is monetarily, gameplay and story-wise. So many modern adventure games are based on this one game. It’s the game that finally made target tracking in 3D work. It’s so well thought out, that a blind streamer is able to play the game probably better than I ever will. If most common people know of “zelda” it’s because of this game. There are so many memes from Zelda in general. It’s one of the few games from my childhood that I will replay for the rest of my life.