Project Gotham Racing 2 ➔ Geometry Wars

OK, so admittedly this one is slightly stretching the remit here. Technically, the smash hit Geometry Wars wasn’t an independently released game before its deeply peculiar appearance in Project Gotham Racing 2. Instead, it proved so popular as a hidden bonus that it saw its own separate release after, going on to spawn sequels of its own.
Bizarre Creations (RIP) released PGR2 in 2003, as an Xbox exclusive. The racing game elaborated on the previous game’s focus on Kudos points, fast-driving, and car collecting, as well as adding an arcade cabinet to the player’s car garage.
Now, this is nothing especially original, and collating all the fictional arcade games that appear on machines in games would be a whole other slideshow. But this one sneaks in because the game on board was Geometry Wars, and players were finding themselves spending as long with this top-down shooter as they were driving cars.
It was so popular that not only was the arcade game released two years later as its own product, but it was one of the launch titles for the Xbox 360. In fact, it was a highlight in a particularly dreadful collection of launch games. The arcade fun of a twin-stick shooter, with its wonderful effects and note-perfect delivery of waves of enemies, was ludicrously sticky.
Geometry Wars of course has gone on to receive multiple sequels of its own, although tragically Bizarre Creations’ successor, Lucid Games, didn’t have the good sense to put one of them into this year’s Destruction AllStars.