EDF! EDF! EDF! There is one central thing you need to know about Earth Defence Force: it is not what people have come to believe they want from a videogame. Graphically it's last-generation, the animations are like watching stop-motion puppetry, the voicework sounds like extras from Baywatch reading the script of an Ed Wood movie, and the monsters appear to be based upon stock photography of insects.
It is, however, the answer to why we started playing videogames in the first place, all those years and all those consoles ago. It is the grand, raw, silly joy of pressing buttons and watching crazy, fantastical stuff happen on the screen in response. For whatever reason - accident, design or budgetary restrictions - it isn't a whole lot more than that. It doesn't need to be. You press a button and a building explodes. You press a button and a dozen giant ants are hurled into the air. You press a button and you ride a speeder bike over the head of a giant robot with laserguns for arms. That is why we play videogames.
EDF: not, in fact, a gas company, but rather the Earth Defence Force, humankind's last, best protection against an invading alien force. Not that they seem entirely sure it is an invasion - they immediately nickname the shiny spheres that appear in the skies 'The Ravagers', and then wonder if they come in peace. A self-fulfilling prophecy, really. The dialogue is hilariously broken and inappropriate, but it adds beautifully to the general B-movie air. "A bug! A very huge bug!"
And very huge bugs they really are - tank-sized ants, shed-sized spiders... It'd genuinely be a little creepy, if only there weren't so many of them on-screen at once that it plunges into happy absurdity. Armed with a rocket or grenade launcher, you murder them in their dozens, strangely undamaged, unwobbling corpses flying skywards and landing as temporary, chitinous mountains. It's low-tech for sure, but the scale and butchery of it looks incredible. EDF was met with a sour reaction by many gamers, and frankly it's baffling that they didn't find this simple act of comical carnage endlessly satisfying.
Equally crucial to EDF's towering achievement is the Police Academy-esque incompetence and total disregard for anyone else of the player-character. Boom! Oops, there goes that bridge. Kapow! Gosh, hope no-one was still in that tower block. Kerrrash! Oh come on, there was no way I wasn't going to shoot that massive radio tower. If it's a building, it can be destroyed. No-one will ever tell you off for it, no points will be deducted and, frankly, nothing will have been achieved - except the pure glee of meaningless destruction. It'd be an entirely different game if there civilians in them, but save for you, perhaps your co-op buddy, the Ravagers and some comically inept AI EDFers (who can also be casually murdered without consequence), the Earth you're so forcefully defending is a ghost-world.