I'm wondering, how can you name the only best game? There are a lot of excellent games, for single-player offline, SP online, and cooperative. A lot of genres. I can name a lot just RPGs, which are much better than watching serials, shows, etc. Maybe I can name the most impressive game, but still - there are a lot of them from different periods of life.
Overwatch. it's way better than Call of Dooty. you can see enemies more clearly and they aren't hiding in dark corners of a room where you can't even see them
I have favorites, but I won't say "best" really. Honestly, I find that having a healthy rotation of games is the best thing you can do because then things feel less grindy, you get a lot of different experiences (or exercise different skill sets), and get to experience many worlds.
Tetris But honestly ... I don't know. During these several years of playing, there were various titles. The ones that once seemed brilliant - as I look at them now, they look downright ... pathetic. I remember the first Tomb Rider or Resident Evil on PSX - how WOW it was. How beautiful it was. And now ... square faces, zero physics and no realism ... but those were different times.