Most conversations about playable loading screens begin with Ridge Racer, likely because the it was the first one most gamers experienced. Ridge Racer was a PlayStation launch game that really showcased the new hardware, and while players waited for the fancy arcade port, they were treated to about 10 seconds of Namco’s classic Galaxian. The coin-op shooter was fully playable as you waited for a race to load, starting Namco’s practice of minigames within load screens.
The Galaxian demo is so well known that Sony’s Kaz Hirai talked it up during his infamous E3 2006 appearance, so it’s unfortunate that so few developers have replicated it, though there’s a good excuse. Namco has the exclusive patent on these types of load screens, so legally no other developer can put them in their games. Supposedly the patent runs out in 2015, so maybe by then we’ll see more minigames like Ridge Racer’s, but that’s no excuse for why Namco hasn’t made all of its loading screens as fun as this one.