Commander Keen (Series) vs Natural Selection (Series)

Commander Keen is a series of side-scrolling platform video games developed primarily by id Software. The series follows the adventures of the 8-year old genius Billy Blaze, using his homemade spaceship to travel across the galaxy under the alias Commander Keen.

Natural Selection is a mod for the first-person shooter Half-Life that eventually turned into a full stand-alone game. It features complex real-time strategy gameplay with two opposing alien races fighting for control of territory and resources.