The Origins of Pong
Gamasutra is running a feature about the origins and development of Pong, and how it helped to kick start the gaming industry. Quoting:
"... games found their way onto even the earliest mainframes, starting the ongoing trend of implementing video games wherever a viable platform presented itself. The first known instance of an actual implementation was Alexander Douglas's 1952 creation of OXO (also known as Naughts and Crosses), a simple graphical single-player-versus-the-computer tic-tac-toe game on the EDSAC mainframe at the University of Cambridge. Although more proof of a concept than a compelling gameplay experience, OXO nevertheless set the precedent of using a computer to play games. The first known precursor of Pong debuted in 1958 on a visitors' day at the Brookhaven National Laboratory in Upton, New York. It was there that William Higinbotham and Robert Dvorak demonstrated Tennis for Two, a small analog computer game that used an oscilloscope for its display."
on the very article you linked to, even OXO was predated by a missile game in 1947 http://en.wikipedia.org/w/index.php?title=History_of_computer_and_video_games&oldid=50887750#The_beginning