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.
I would usually have said Earthbound or Chrono Trigger, but this year I've been playing Sea of Stars and it truly seems better. I never thought I'd say it. The writing, art, music, gameplay, movement, puzzles, characters, all are aimed in the exact same direction as what CT was trying to do and it goes farther in every way.
They were pretty deliberate about having very similar creative aims, standing on the shoulders; they even got Yasunori Mitsuda to help with their soundtrack. The game keeps on surprising me with its self awareness, beauty, and a depth of gameplay that keeps unfolding long after you think you have the measure of it.