Individual Earth Defense Force releases generally receive mixed or average reviews, but the series has been lauded for its simplistic but entertaining premise and campy tone, and it maintains a strong cult following.

The vast majority of Earth Defense Force installments are set after the discovery of the Ravagers, an intelligent and organized alien race, with the formation of the EDF sometimes explained as being a precautionary measure.

The game's playable characters are represented by different character classes ("armors") that vary depending on the game, but across most entries the basic armors are the "Infantry"/"Trooper"/"Ranger", a standard all-rounded soldier wielding standard service weaponry and explosives; the "Pale Wing"/"Wing Diver"/"Jet Lifter", a female special forces scout with a light but vulnerable jet-powered winged suit; the "Fencer", a support soldier in a heavy but slow exoskeleton wielding heavy guns, powerful swords, and usually also a ballistic shield; and the "Air Raider", a logistical technician reliant on controlling close air support, drones, and requisitioning usable combat vehicles such as tanks, infantry fighting vehicles, helicopters, hoverbikes, and mecha.

[6] It essentially retells the events of the 2017 invasion depicted in Monster Attack, from the perspective of Storm-1, an elite Japanese EDF unit that spearheads the fight against the aliens.

Chikyū Bōeigun 4, released overseas as Earth Defense Force 2025, is the fourth main installment, developed by Sandlot for the Xbox 360 and PlayStation 3.

Chikyū Bōeigun 5, released overseas as Earth Defense Force 5, is the fifth main installment, developed by Sandlot for the PlayStation 4 and Microsoft Windows.

Earth Defense Force: Insect Armageddon is a spin-off developed by Vicious Cycle Software for the Xbox 360, PlayStation 3, and Microsoft Windows.

Earth Defense Force: World Brothers is a voxel graphics spin-off developed by Yuke's for the PlayStation 4, Nintendo Switch, and Microsoft Windows.

[23] The game features a similar plot to the original World Brothers, with the EDF investigating another shattering of Earth, this time caused by the Gaiark, an entity within the planet itself.

Joe Juba of Game Informer defined Earth Defense Force 2017 as a cult classic, stating that "the developers at Sandlot clearly want to tell a story about humanity's struggle against giant invading ants and robots, and the passion for that story shines through despite its technical shortcomings";[35] in reviewing Earth Defense Force 5 five years later, he similarly opined that the series has "always had a single-minded commitment to one simple truth: It's fun to use weird weapons to blast lots of aliens.

"[36] Though James Stephanie Sterling gave Earth Defense Force 2025 a negative review, she did acknowledge that the series "has managed to earn itself a fierce cult following through audacity alone".