As another grey, rainy British summer slips seamlessly into a grey, rainy British autumn, I start to think about game environments, and how developers now have the power to create believable new worlds.

Let's face it, games are a fantastic kind of escapism - particularly in dreary autumnal evenings - and the processing power of current gen consoles and PCs allows gamers to experience vibrant virtual spaces in more detail than ever. With this in mind, I tried to come up with a list of games with genuinely memorable, imaginative worlds, and came to the surprising conclusion that the vast majority of them lack this.

Of course, there are plenty of games that are still fantastic despite their environment's lack of personality; take Gears of War, for example. Now, before readers start leaving irate messages about how graphically stunning this game is, let me explain exactly what I mean. Yes, GoW's 'shattered beauty' is extremely well depicted - indeed, it's still one of the best looking games on the 360, even two years on - but it's not what I would describe as imaginative. As detailed and carefully wrought as the devastated buildings and burnt out cars are, it doesn't change the fact that for large portions of the game you're blasting a horde of grey, Rancor-like enemies among grey chunks of concrete with grey clouds rolling overhead. In fact, GoW only gets really colourful when you let rip with your lancer and spatter blood on the camera.

In no way is this a reflection on GoW's playability or its otherwise top-drawer quality (one of my favourite blasters of all time, in fact), but it does illustrate my point: as good as GoW is, is its setting as genuinely memorable as, say, Bioshock? I would argue that it isn't.

In many ways, Bioshock is inferior, in pure gameplay terms, to Gears of War. While it's a solid enough FPS, it's pretty simplistic underneath all the plasmids, 'moral' choices and gimmicky Pipemania subgames. Without its engaging story and unique setting, it's quite likely that Bioshock would have sunk without trace. It's the surreal world of Rapture, full of long shadows and flickering neon, that make the game so special.

Similarly, Fumito Ueda's Ico is a game that sticks firmly in the mind thanks to its tangible sense of place. I haven't played it in at least four years, but its spooky, de Chirico-inspired castle full of impossible architecture and lush green gardens is still as fresh in my memory as if I'd only played it yesterday. It would still have been an eminently playable game without its exquisitely wrought world, but I have a feeling that its cunning puzzles and princess protection would have been considerably less engaging.

Creating immersive worlds is clearly Ueda's forte since his follow-up to Ico, Shadow of the Colossus, had an equally impressive setting, with stunning vistas that seemed to stretch to infinity. Its eerily desolate world was so compelling, in fact, that it cunningly papered over the game's unavoidably repetitive nature and the stuttering frame rate as the poor old PS2 was stretched to its technical limit (one can only imagine how beautiful Colossus could have looked had it been created for the PS3 instead).

It's not necessarily true that a game world has to be vast in scale to be memorable though; Number None's Braid creates a uniquely atmospheric environment with relatively simple (but visually stunning nonetheless) 2D graphics.

The antithesis of Braid has to be Square Enix's Infinite Undiscovery, which I reviewed  earlier this week. The game features a sprawling map that wouldn't even fit on one DVD, and an expansive cast of characters to match. Unfortunately, a thirty-hour campaign and a huge map failed to create a particularly memorable setting - instead, Undiscovery felt like a cliched grab-bag of references to other RPGs without them gelling to form something new.

A truly memorable game world is difficult to define, and something of an 'x-factor'; it doesn't necessarily have to be original (all the games I've mentioned so far borrow elements from all kinds of popular culture, after all), and it doesn't have to be gigantic in scope or even technically stunning (see Braid).

Like a good novel, the best game worlds seem to take on a life of their own - it's as though they continue to exist even after you've turned off your console. Whether its the towering architecture of Ico, or the eerie desolation of S.T.A.L.K.E.R, certain games have an unforgettable setting that lingers in the mind long after the power's been turned off and the disk has been put back in its box.

Ryan writes his gaming column every week at Den Of Geek. Last week's is here.