Do you mean "best video game of all time" as in like our favorite...or just a general best of all time?
I'll answer both to be safe...
-My favorite: Romance of the Three Kingdoms 8. Hours upon hours upon hours of gametime/re-playability, makes you think while at the same time can be insanely entertaining, looks very well for a game made in the year it was made (I think 2002?), and gives you a great Romance of the Three Kingdoms feeling (which is awesome for me, because that is my favorite book, which is based off of my favorite time period in history)
-Best game: Pong. Yes..Pong. It revolutionized the entire industry of video games, is insanely addicting, and yet is the most simplistic game of all time (Seriously, the amount of fun you can have with 2 rectangles and a square is pure awesome-ness)