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.
Quake 3 arena on Dreamcast. 4 player split screen with low gravity and unlimited ammo turned on was something that controlled me and my group of friends lives for years. Not the best game ever to some but definitely to me. Also to get the low gravity and ammo unlocks you had to play a huge maze on the vmu screen. We spent hours mapping out those mazes 1 square inch at a time. They were literally enormous but you could only see 1 inch at a time on that tiny but genius vmu. We even carried our controllers everywhere just in case a game broke out at a party. Each controller was customized with sharpies and shit too. Miss those days so much.
Unreal Tournament on Dreamcast was amazing too. I played online non-stop.
Unreal was def in rotation but quake was always our preference.