Earth Defense Force 2017 is like that really slutty girl you went to high school with: They're both cheap, they provide roughly five hours of entertainment, and there's the terrifying chance that they'll cause you to lose your genitals to a swarm of insects.
EDF 2017 seems like a parody of all of those Japanese "man vs. giant insect/robot/lizard" movies that were so popular in the post-Cold War era—but after playing through the 50-plus missions of this game, I've come to realize that Sandlot, the developers, are totally serious about this whole thing, which only adds to the appeal of the title.
The basic premise: Aliens have decided to take over Earth, coming up with the wise strategy of utilizing an army of giant bugs, robots, and dinosaurs equipped with rocket launchers. You're the only one who can stand in their way, and you'll be outfitted with a ridiculous amount of high-caliber weapons, and the only time you should stop firing is when you need a sandwich or have to pee really badly.
EDF 2017 succeeds for two reasons: First, there's nothing else like it on the Xbox 360. (One of you dickfaces is going to whine, "Oh yeah? What about Ninety-Nine Nights?" to which I'll respond, "Fuck you!" and then point out that action fest Ninety-Nine Nights didn't have a SINGLE giant spider attack.) The second reason EDF 2017 works is that the game's utter Michael Bay-ness—explosions and pyrotechnics are everywhere—is almost unmatched. There are moments that'll make you scream, "Yeah! What now, bitch?!" at your TV, much to the dismay of your girlfriend/dog/congressman.
Obviously, there's little variety to what you're doing—so if you pick up EDF 2017 hoping it'll have things like "a plot," you're going to be disappointed. On the other hand, it's only $40, so you could definitely do much worse as far as Xbox 360 titles go. (Ninety-Nine Nights, I'm looking at you.)