Like dynasties rising and falling, videogame systems enjoy periods of ascendancy and popular support, only to be thrust aside by a new and conquering power. First came Magnavox Odyssey (in the 1970s), then Atari consoles, then Nintendo, which dominated the market for the better part of the 1980s. In the early 1990s, Nintendo's Super NES and Sega Genesis battled each other for supremacy. Each found enough competitive room to lay the groundwork for the modern videogame console, which has become something like a dedicated personal computer.

It...