All video games tap into our obsessive compulsive nature to some degree, but few do it more ruthlessly than the loot-dropping dungeon crawl RPG. This is a genre for people who feel a deep sense of personal failure if they don't smash every barrel, open every chest and own an inventory groaning with Rare Inferno Pantaloons of Swiftness.

It's also a genre that is making a comeback, with Torchlight stripping the formula down to its ruthless core components and Diablo III bringing back the sense of a blockbuster event to a game style that was once in danger of falling out of favour.

Dungeon Siege slots into the space in between these two extremes. Never quite big enough to attract Diablo-level passion (the movie adaptation fell to Uwe Boll, after all), but too ambitious in scope to fit comfortably with the new download aesthetic.

As it turns out, Dungeon Siege III looks set to define the middle ground. In a good way. Based on ten hours of roaming around the latest preview build, it looks like a robust, well-paced and carefully balanced dungeon crawl with a decent storyline and a journey that takes you through dozens of varied environments.

The story picks up some time after Dungeon Siege II. The kingdom of Ehb is mired in civil war. The 10th Legion has been decimated, its few remaining soldiers scattered and hunted by the cruel Jeyne Kassynder. As one of those few, it's your job to rebuild the Legion and lead the rebellion against Kassynder's zealot army.

Four characters are waiting to take you on this journey. You choose one as your main character, with the other three popping in to join your team as you go along.

There's Lucas Montbarron, son of Hugh Mountbarron, last Grand Master of the Legion and your typical sword-and-armour melee fighter. Anjali is an Archon, a fire demon with no memory of how she came to Earth. Raised by the Venerable Odo to fight for good, she's basically Hellboy crossed with the Human Torch and a set of boobs.

Reinhart Manx is a Legion mage with a reputation for unusual spellcasting. Finally there's Katarina, a Lescanzi witch specialising in firearms and ranged attacks. She's the illegitimate daughter of Hugh Montbarron and therefore Lucas' half-sister.

Between them they cover all the class types made popular in the prior Dungeon Siege games. This time, however, you're only ever controlling your chosen character. Once recruited you can switch your companion at any time, but this is strictly a two-handed affair. No four-way Gauntlet-style monster mash-ups, unfortunately.

Controls have been intelligently streamlined for console play, with the d-pad offering shortcuts to the most useful menus. A prod left calls up your list of active quests, while right takes you to the equipment screen. Up conjures a Fable-style breadcrumb trail for whatever objective you're currently working towards. All interactions, from looting chests to initiating conversations, are carried out with the right bumper.

For combat, blocking is mapped to the left trigger and there's a simple one-button attack that's modified by two different stances. These are quickly alternated with the left shoulder bumper.

Lucas swaps from two-handed broadswords to a more traditional sword and shield combo, Katarina from ranged carbine to a dual-wielded shotgun and pistol combo. Anjali can choose from her agile human form and a more destructive fire form.

From there things unfold much as you'd expect for a top-down RPG, with giant spiders lurking in forests, travelling merchants offering a discount once you save them from bandits and rural wives sending you off to find their missing husband in the Gloomy Caves of Goblin Death.

But it's hard to be too cynical about the genre cliches Dungeon Siege deploys since it gets the mechanics so enjoyably right. While the game never matches Torchlight's manic pace, it certainly doesn't hang around. It's almost episodic in nature, introducing a new location, along with new enemies and fresh quests, every hour or so.

The story rattles along at an agreeable clip, never bogging you down with too many optional objectives, and your character evolution follows suit. In about seven hours of gameplay I'd managed to reach level 14 and the meat of the story was only just about to kick in. Companions level up alongside you, and as you tweak and enhance their various abilities and proficiencies you can exert a small amount of influence over their combat style.

Visually, the game does a good job of showcasing Obsidian's Onyx engine. Environments are rarely interactive, but they are lushly designed and boast some subtle lighting effects.

From gloomy forests to eerie abandoned mansions, quaint villages to urbane cities, there's an appealing feel to the world of Ehb. It all flows seamlessly as well, with no loading screens. Your jaunty trot simply slows to a walk while the game loads in the next area.

It's a pity the same polish isn't evident in the characters populating the conversation scenes, where you pick responses with a Bioware-style chat wheel. Faces are stiff and the voice acting, while more than adequate, doesn't have enough personality to compensate.

Despite this, the game itself is surprisingly funny, with lots of pithy descriptions and sly in-jokes for fans. Most notably for those who loved the previous game and it's lovable roving inventory system, there's the "pitiful corpse" of a mule left by the roadside, crushed by the weight of "many suits of armor, sacks of gold and impractically large battleaxes".

Elsewhere a mechanical constable, basically a steampunk Robocop, boasts of providing "feline wrangling services" along with his violent law enforcement duties. In another particularly daft moment, you meet a character called Baron Barrenbaron.

Dungeon Siege III clearly isn't setting out to redefine its genre, but it has a finely balanced sense of its own strengths and seems to have nailed the addictive tug that all loot drop RPGs must possess. Quests unfurl into one another organically and there's always something new around the corner, offering a reason to play for another half hour, then another, and another...

And that's without access to the online co-operative mode, where players get to vote on conversation responses as well as battling side by side. Roll on next month, and a distinct lack of sleep.