Chess, probably. Or some kind of card-involved game, I presume. Those have been around for quite a long time, and they are still enjoyed by a lot of people, so they can probably be considered the most popular games.
Cenere is correct while thinking of using no technology. When speaking in terms of consoles and other such, the Mario series. While they might be over doing Mario today, he is still the most popular video game character, along with the most popular series. This might be better in the gaming section?