This was the video game debut of that annoyingly-cute Italian plumber Mario.
The plot: Donkey Kong has kidnapped Mario's girlfriend and stuck her (a la King Kong) on top of a structure. It's up to Mario to save her, and save her, and save her, etc... (DK was a "wave game" which didn't have an end, it just got harder and harder.)
Sequels:
Donkey Kong Jr.
Donkey Kong 3
Mario Bros.