Old Games

The oldest backgammon in the world along with 60 pieces has been unearthed beneath the rubbles of the legendary Burnt City in Sistan-Baluchistan province, southeastern Iran.

Iranian archeologists working on the relics of the 5,000-year-old civilization argue this backgammon is much older than the one already discovered in Mesopotamia and their evidence is strong enough to claim the board game was first played in the Burnt City and then transferred to other civilizations.

Iran Oldest Game, "Backgammon" (via Boing Boing)

Which therefore clearly beats go in age.  However the title of oldest known board game still probably goes to Senet.