Operation Darkness does one thing wrong, and a whole bunch of other things right.
Most importantly, it tells a gripping story. World War II is a pretty epic tale by itself, but adding vampire Nazis and British troops who also happen to be rocket launcher-toting werewolves is the sort of genius storytelling you only get from independent Japanese studios unconcerned with appeasing shareholders. Also, they somehow toss dragons and zombies into the mix. I could explain how that works, but your mind would probably explode from the sheer radness of the concept.
Wisely, developer Success opted to hire some extremely talented (for the gaming industry) voice actors to help move the story along. Performances aren't Oscar-worthy, but they're believable and never distract from the compelling storyline.
Unlike many other strategy titles that require a doctorate to play, Operation Darkness keeps the gameplay simple: Everything boils down to moving characters on a grid and selecting actions when asked. It'll probably prove too slow for the ADD crowd, but if you can focus for more than 10 minutes, the gameplay proves deceptively complex and rewarding.
In a surprising move, Success also added online cooperative gameplay. That's an option that's almost unheard of in the strategy genre, but allowing gamers to play with friends is always a nice touch.
The only downside to the thing is the lack of polish in its aesthetics. All of the 2D artwork has a gorgeous, gritty anime style, but in trying to translate that look to 3D, the developers inadvertently created characters, buildings, and vehicles that look cheap and rushed. Combined with the graphical slowdown found in every mission, it's obvious the game lacks the polish it really deserves.
Still, how often do you get to wage war against Nazi vampires with a force of British werewolves and fire wizards? Operation Darkness' flaws aren't nearly big enough to override the game's insane storyline, and while it won't have much mainstream success, Operation Darkness is the next "best game no one's ever played."