While fans of mindless run-and-gun shooters sit around salivating all over themselves in anticipation of Bungie Studio‘s Halo 3 (set to be released on Sept. 25), the rest of the video gaming world has had Aug. 21 circled on their calendars. Today, 2K Games Boston (formerly Irrational Games) releases its first-person-shooter-and-RPG-hybrid, Bioshock—-which some print and Web publications have already declared as “Game of the Year.”

The Bioshock demo, released through Xbox Live on Aug. 12, introduced the game’s storyline: Set in 1960, players assume the role of a plane crash survivor who is floating amongst the flaming wreckage in the middle of the Atlantic Ocean. After swimming your way toward a nearby lighthouse and using a transportation device located inside to travel to the ocean floor, the player is greeted by the Art Deco-inspired underwater metropolis of Rapture—-a utopian city, designed by Ayn Rand-esque megalomaniac Andrew Ryan, where society’s brightest artists, scientists, and industrialists would not have to “fear the censor,” “be bound by petty morality,” or “be constrained by the small.” In Rapture, Ryan explains during the short film projected on the interior of the transportation unit as you delve further into the dark depths of the ocean, a man is “entitled to the sweat of his brow.” Yup, Rapture seems like a pretty swell place—-until you arrive at the docking station and discover that everything has gone terribly wrong.

The demo was enough to induce a fervor of excitement among fans of the game’s spiritual predecessor, System Shock 2, who, after months of hype, had begun to worry that their expectations had been set impossibly high—-only to discover that, not only had those expectations been met, they had been surpassed. The buzz continued to grow when, three days later, news broke that Toys “R” Us had begun “accidentally” selling copies of the game in advance of the Aug. 21 street date. By the time the retailer issued a statement in which it claimed that Bioshock had been yanked from the shelves, video game bloggers had already posted photos of their advance copies and accompanying reviews.

The early verdict, which has since been echoed by popular video game review Web sites such as IGN.com and GameInformer.com, is universal: If you own an Xbox 360, you owe it to yourself to get Bioshock—-and if you’re a PS3 or Nintendo Wii fanboy who doesn’t own an Xbox 360 yet, you now owe it to yourself to get one. IGN.com gives it a stellar 9.7; the average press rating based on 19 other respected sites is an even more impressive 9.8. So far the only “negative” review comes from Gamespot.com, which—-after citing a few technical glitches and overall ease of play—-gives the game a 9.0 rating and an “Editor’s Choice” award.

So, what makes Bioshock so good?

The shooter and RPG aspects of the game are certainly on par with the best games in the genre; both provide a satisfying amount of depth and customization without being overbearingly complicated. The graphics and sound are also top notch—-if you don’t have a high-definition television and a surround-sound setup, Bioshock is one of the best reasons you’ll have this year for getting them. (The oft-praised rippling effect of the water—-which, considering that the game takes place underneath the ocean, there’s a whole hell of a lot of—-is the best ever seen on a video-game console to date.) And the moral decisions you are forced to make, such as choosing whether or not to murder the ghoulish “Little Sisters”—-genetically-modified prepubescent girls who collect and carry the game’s much-coveted energy source, “Adam”—-to increase your power have consequences—-namely, how many of the hulking, drill-equipped “Big Daddies” you’ll have to square off against as well as the nature of the game’s conclusion.

Yes, those aspects of the game are fine and dandy. But the real draws of Bioshock, however, are the compelling storyline (which contains its fair share of obvious and not-so-obvious plot twists), voice acting (players discover the fate of Rapture’s inhabitants by listening to random audio diaries), and the city of Rapture itself—-a neon-lit dream city turned nightmarish abomination whose potential is exceeded only by its colossal failure. Whereas in other shooters and RPG’s many of the locations are simply nondescript caves/hallways/dungeons in which you run around killing generic enemies until you’ve leveled up and gained enough money to upgrade your indistinguishable weapons/armor before moving on to the next cut-scene, Rapture is a legitimately creepy place that continuously holds your imagination, forces you to actively explore, and rewards you for doing so.

In the end, that’s what will likely make Bioshock the game of the year: Not that it’s just the best in its genre, but it redefines the genre—-and players’ expectations. Sure, it doesn’t have a tacked-on online multiplayer mode. But it doesn’t need one. Bioshock works as a piece of interactive fiction, a slow-moving mystery so well-conceived and followed-through that it brings up the age-old argument of whether or not video games can be considered works of art.