Which shooter arcade game defined its genre?

[killamch89]

When considering shooter arcade games that defined their genre, I return to Space Invaders. Released in 1978, its simple yet addictive mechanics of shooting alien formations, combined with the changing enemy speed, set the standard for future vertical shooters. Galaga expanded on this foundation by introducing enemy capture mechanics, and 1942 brought forward a World War II backdrop and player-controlled roll maneuvers. Which arcade shooter do you feel truly defined its genre’s conventions, innovations, or aesthetics?

[Scorpion]

Space Invaders arguably defined the arcade shooter genre. Its simple yet addictive gameplay, wave-based enemies, and iconic sound effects set the standard for countless titles that followed.

[killamch89]

Defender's multidirectional scrolling, complex control scheme, and strategic depth redefined what arcade shooting could be. By introducing radar awareness, hostage rescue mechanics, and smart bombs, it transformed shooting from simple reaction testing to a complex strategic exercise requiring total situational awareness.