1. Advance Wars: Days of Ruin (Nintendo DS)

You know how they say what doesn't kill you makes your stronger? How about really, really depressed instead? Who wouldn't be if a couple rogue meteors kicked up a sun-blotting dust cloud that draped the planet and rubbed 90 percent of the Earth's populace off the map? The only upbeat tick in Days of Ruin's gloomy plot involves saving scattered survivors while thwarting gangs of private military contractors (including one engaged in biological experiments on the populace) in brisk, turn-based tactical battles to ensure humanity's survival until the dust cloud clears off.

2. Command & Conquer 3: Tiberium Wars (PC)

Actor Joseph Kucan conjures just the right amount of "raving spiritual lunatic" for this real-time strategy game about a terrorist madman named Kane (played by Kucan) leading a cabalistic brotherhood and battling a power-mad "global defense initiative" in a race to control an alien power source called Tiberium. Green, glowing and screaming "metaphor for nukes," Tiberium helps fuel both sides' war engines while simultaneously poisoning the planet. The Tiberium infestation gradually blights the Earth's ecology, dividing the planet into uninhabitable red zones, yellow zones (pretty dangerous, but—surprise!—harboring most of the world's population) and safe blue zones. Enter the aliens themselves as the game's third faction, and you've got an ecological brouhaha that's like Al Gore versus Rush Limbaugh versus Ralph Nader in a latex Giger suit.

3. Crysis (PC)

The great thing about hostile aliens is, they rub all the moral ambiguity out of an issue. Climate change? Scratch SUVs and bovine belches and blame it on a bunch of pesky extraterrestrials that look unrepentantly like Geofrey Darrow's octopod sentinels in the Matrix movies. Oh, and instead of global warming, we're talking a plague of ice and snow and even a little gravitational meddling to put some bounce in your pounce. In Crytek's first-person sandbox shooter Crysis, that's the ecological disaster, and you're invited—you, your Gauss rifle and a set of super-duds with which you'll perform feats of derring-do looking like Steve Austin in a wetsuit. The action happens so fast you'll get frostbite on your sunburn battling an alien menace bent on deep-freezing the planet as prelude to an invasion.

4. The Simpsons Game (multi-platform)

At one point in the stream-of-hilarity ramble that makes up The Simpsons Game's plot, Lisa and Bart discover that Mr. Burns has built up a titanic logging facility (appropriately dubbed "Aunt Eco, Environment-Friendly Logging Site") designed to effectively deforest the planet and replace every tree with "a single luxury toothpick." Bart and Lisa have to use their special powers to destroy the facility and save Lenny and Carl from death by sawblades. Title of this particular mini-episode? "Lisa: The Tree Hugger."

5. Undertow (Xbox Live)

An aquatic alien race secretly launches attacks on Earth, melting the polar ice caps and basically turning the planet into Waterworld. Instead of growing gills and webbed feet and putzing around in a boat, trading with atoll dwellers and tossing road flares at pirates that look like Dennis Hopper with a socket-popped eyeball, human Iron Marines battle Nemoidians and Atlanteans in what amounts to an underwater shooter with teams taking and holding checkpoints to rack up points and win matches.