Tetris. No question.
Let me explain. There are very few games whose very concepts are SO perfectly, optimally, simplistically ideal that you can reasonably say the game concept was "discovered," not created. Even fewer of these games are addicting enough to even be worth naming, or being recognized at all. And only one of these has stood the test of time and quality so well that it is named among video game juggernauts like Minecraft, Mario, and Pokemon.
Tetris. It's nearly 40 years old. It's literally a game about falling blocks that could be written in a hundred lines of code. Yet it's 9th best selling game of all time. Yet it was so addictive that it escaped the iron curtain of Soviet Russia. Yet it sustains large competitive community whose tournaments are broadcast on ESPN. Yet it's a game that continues to beat conglomerations, corporations, round table concept artists, game developers, graphic designers, and greasy media moguls and continues to win all our hearts.