Twilight Struggle
"Twilight Struggle" was the highest-ranked game on BoardGameGeek from December 2010 to January 2016. As of August 2018, the board game occupies a fifth spot. Being released in 2005 it is the oldest board game in the overall top 10 ranking.
Immortal Game
The Immortal Game was a chess game played by Adolf Anderssen and Lionel Kieseritzky on 21 June 1851 in London, during a break of the first international tournament. The bold sacrifices made by Anderssen to secure victory have made it one of the most famous chess games of all time. Anderssen gave up both rooks and a bishop, then his queen, checkmating his opponent with his three remaining minor pieces. In 1996, Bill Hartson called the game an achievement "perhaps unparalleled in chess literature".