For me it was the original Modern Warfare 3. I played that campaign a lot as a kid, but didn’t have internet back then so no multiplayer and no one to discuss the game with. The story is dumbed down compared to the first two games but it was pure fun and cinematic, every mission was memorable to me.

Like I didn’t even know what the stock exchange was back then, I just thought it was awesome traveling through city ruins fighting invaders.

Also the survival mode was super fun too.