There are lots of things to celebrate in Far Cry 3, Ubisoft's best game since Assassin's Creed: Brotherhood, but the thing I keep coming back to is Rook Island itself. There's often a lot of unremarkable space in open-world shooters, but this vast, mountainous patch of fictional grass and rock in the middle of the Pacific has been created by people who believe that every inch is important, and who have refused to compromise or sculpt any part of it with less than an artist's attention to detail.

There are 18 radio towers to scale as you make your way through the game, each of which highlights new objectives on your map and opens up new weapons to buy at local shops, and each tower is a unique first-person climbing challenge - a peaceful ascent through a creaking spiral of steel that's fraying at the edges, revealing beautiful panoramic views before sending you back down to earth on a thrilling zipline.

There are over 30 enemy outposts to stalk and reclaim, each of which gives you a new safehouse and reduces enemy influence and presence in the surrounding area, and while there's some familiarity in layout, each is woven carefully into its surroundings - recessed into the foot of a mountain surrounded by jungle, perhaps, or swaddled in corrugated iron at the top of a hill, or perched on a rock at the edge of a wide beach approach.

Every forest is home to some species of wild animal, some of whom are definitely not more scared of you than you are of them; every road winds past shacks full of loot; every peak is home to a hang-glider; every cave or abandoned military fortification is an excuse to pick through the island's history. You begin the game in the frightened shoes of Jason Brody, a tourist on a dream holiday gone horribly wrong, but by the time the credits roll you won't want to leave this broken paradise.

Taking down outposts will be the core of the game for some people. It's a tasty core.

Jason's story and the way it is told sometimes veers a little too close to the kind of scripted matinee adventure more familiar to corridor shooters and Uncharted-style action games - and there's an uncomfortable period right at the start of the game where it's in such a hurry to get the tutorials out of the way that everything feels very contrived. Both flaws are easily and quickly shrugged off once you settle into Rook Island's rhythm.

Perhaps it's because those sections of the game make you feel subservient that they don't work as well, in fact, because for most of the rest of the game you feel like the king of the jungle. No-one or nothing is a match for you when you get going; when the game tells you that you need shark skin to upgrade your wallet capacity, you wade out into the ocean and punch the nearest Mako to death.

The outpost assaults - and similar, smaller-scale Wanted missions where you have to assassinate a local pirate or privateer with a ceremonial knife - are probably my favourite things about Far Cry 3. Approaching the base from a distance, you find an elevated vantage point or bed down in some nearby shrubs and use your binoculars to scope out and mark targets as they stand guard or patrol the area. Then you advance.

Fans of open-ended stealth are in some kind of heaven here. Moving between the concealment of bushes and obscured sight-lines, watching the silhouettes of marked enemies move around on the other side of scenery, you can pick off the weaker ones as they become isolated, or maybe toss a stone to tempt them out of position. As you gather XP and unlock new abilities on the skill tree you can chain together takedowns, popping up to cut one guy's throat before pulling out the knife and throwing it at the next guy's head.

"Fans of open-ended stealth are in some kind of heaven here."

The stealth system is immaculate and hyper-violent.

The outposts you take down by disabling alarms and never being spotted are the most satisfying, but you don't have to do that by knife alone. You can plant landmines where you know someone will wander, or shoot the door off an animal cage to let loose a bear or tiger, who may do most of the work for you, or you can start a fire with your trusty flamenwerfer.

Sometimes things don't go to plan, but that doesn't matter either, because you like to use the silenced pistol but you also keep a shotgun handy for close encounters. Or maybe a bow with explosive arrows. The speargun's one of my favourites: it feels most apt when you're climbing onto the deck of a ship and a pirate you missed during recon appears at the first corner and stumbles into your sights. It always pays to have a backup plan too, which is why remote charges are quite handy if you're sailing too close to the edge of your stealthy capabilities.

My favourite bits are when the local wildlife doesn't wait for an invitation to get involved. Yesterday I was stalking through one coastal outpost doing my usual stealth thing - I think I'd just performed a double takedown-from-below on a pair of guards on a dock and was sniffing around for some loot in a shipping container - when I realised I was taking it too easy and a nearby guard was going to spot me in a few seconds. But as I swore and fumbled for my silenced MP5, his silhouette straightened up and spun around, before he appeared to fall back onto the floor and start screaming. I had a look round the corner and discovered he was being mauled by leopards. Rescue leopards!

This stuff doesn't always work to your advantage, mind you. There was also the time I saw a bear prowling around the edge of another outpost and thought I'd try to bring him into the action, so I shot him in the ass and then tried to kite him through the midst of my enemies in the hope he would engage them. Instead they rang the alarm, blasted half my health, and then as I ran away to patch up my wounds the bear appeared in my path and finished me off. So yeah, rescue leopards are handy, but watch out for flanking bear jerks too.

There's no lean function (at least not on Xbox 360) and dragging bodies out of sight is an unlockable ability that's only possible right after you knife someone, both of which are slight annoyances, but the detection system is consistent and apart from the story missions, which are more linear and enclosed, you can generally escape conflict by just running for the nearest hills to regroup.

Vaas may have been the star of the promotional campaign, but he's not the only nutjob on Rook Island you cross paths with.

There's a huge amount of stuff to do besides stalking enemy bases, too. You can kill animals whenever you want (and along with the local flora they form part of an overly complicated subsystem of generating syringes and upgrading item capacities), but there are also specific hunting missions where you need to take down a rare panther with a bow and arrow or sort out a few rampaging bears with a pistol. Or, if you prefer, there are some driving tasks - there are lots of banged-up 4x4s and buggies lying around Rook Island to shorten your travel time and some of them have missions attached to them. There are loads of collectables too. And the more open-ended story missions - like an assault on a pirate ship - are standout moments in a game that is rarely short of them.

A lot of this stuff was true in Far Cry 2, of course, but while that game was also magnificent in its own way, it was a little bit in love with itself in some other respects - which resulted in things like bus journeys, respawning military checkpoints and other ideas that seemed to be more about getting the design to match the setting than making things more enjoyable for the player. Far Cry 3 is a clear reaction to that - there's fast-travel galore, no more respawning, sympathetic checkpointing and lots of shortcuttery - but as well as curing some of its predecessor's ills, it also builds on it spectacularly.

It even spins an entertaining yarn. Jason's initially on a quest to save his captured friends from the pirate boss Vaas - a classic Bond villain, always lecturing you or dreaming up your grisly demise but rarely just shooting you in the head - but your motivation gradually shifts and a series of unusual allies (including a pickled old spook, a bare-chested deviant Aussie and a mad German) send you down some crazy paths and holes in pursuit of progress. The writers also draw a line between your own seduction by Rook Island and Jason's, which helps counter the usual conflict at the heart of open-world games (I'm on a desperate mission to save my friends, but ooh look shiny thing!) and keeps you guessing a bit as well.

Outside the substantial single-player game, there's even a separate four-player co-op campaign to play (split-screen or online), where a quartet of national stereotypes (an ex-heroin addict from Scotland who says "c***" a lot, for example) chase down their former ship captain using a mixture of loadouts, sniping or blasting their way through hordes of pirates, protecting objectives under siege or competing with each other in ATV chases.

"Far Cry 3 is all the best things about open-world gaming."

The more open story missions - like this attack on a rusting shipwreck - are some of the game's best moments.

Then there's multiplayer, which includes a range of capture-the-whatever modes as well as the standard solo and team-based stuff that every FPS now has to include, although I didn't get much of a chance to try this stuff out. And as with Far Cry 2, you can design your own maps and upload them to other players, with the developers set to curate lists of the best user creations as players get stuck into the game.

A separate co-op campaign, multiplayer and a level editor are more examples of Ubisoft going beyond the call of duty (well, going as far as Call of Duty, anyway), and along with Assassin's Creed 3 it's hard to argue that the French publisher isn't offering stupendous value for money at the end of this hardware generation. Never mind the Animus, Ubisoft Montreal must be rocking a time machine in order to ram so much content into these games without missing their ship dates. But while these extras work fine and I'm hardly complaining about their inclusion, in truth they are the least interesting things in a game that would be among the best things I've played this year even if it was just a single-player campaign in DVD box and nothing else except a note saying "have at it".

That's because Far Cry 3 is all the best things about open-world gaming. It's a glorious anecdote factory, where you manufacture brilliant new memories every time you wake up in a safehouse and head out into the jungle. It's an astonishing technical achievement, as comfortable revealing incredible landscapes over the brow of a hill as it is when the setting sun winks at you through a canopy, or when the heavens open as you stalk wildlife through the trees and long grass. And it always lets you play, but it also controls the tempo - sometimes a little heavy-handedly, but always with good intentions.

In the past, Far Cry's vision of a first-person shooter RPG where you explore, master and then control your environment has always been more seductive on paper than any of its developers have managed to deliver on disc. Far Cry 3 changes all that. For me, this is the new apex predator of open-world shooters. Hunt it down as soon as you can.