Ron 'Grumpy Gamer' Gilbert points to a Brookhaven National Laboratory page entitled 'The First Video Game', which documents "employee William Higinbotham, speculating that he may have invented the first video game, with his tennis game of 1958." Indeed, Wikipedia has an entry for Higinbotham's pre-Magnavox patent 'Tennis For Two', devised to run on an oscilloscope after the scientist considered that "...it might liven up the place to have a game that people could play, and which would convey the message that our scientific endeavors have relevance for society."

In fact, according to the webpage: "Tennis For Two was part of the division's exhibit for two years, and it turned out to be a real crowd pleaser. The oscilloscope display in 1958 was only five inches in diameter. The next year saw some improvements: a bigger tube ten or 15 inches in diameter was used, and players had a choice of tennis on the moon, with low gravity, or on Jupiter, with high gravity."

So, even in 1959, gamers had to be upgrading their TV sets and playing sequels, huh? For those interested in trying it out, there's even a Tennis For Two Simulator available.