Imagine you've bought a cake from the finest Parisian patisserie. How many slices would you need to eat before deciding on whether it's good or not?

Don't worry, it's an analogy.

Because it's the kind of question you face when playing – or, specifically, reviewing – Vice City Stories. We'll be perfectly upfront and declare we've yet to finish everything on offer within the vast playground of this improved, second handheld offshoot from the home console GTA games (the first being last year's GTA: Liberty City Stories), despite repeatedly delaying our review to play a while longer.

But, just like when tasting cake, we've sampled enough to know that despite the odd technical niggle (textures and sound have a habit of glitching) and sometimes frustrating missions (whether due to the inevitably convoluted camera system, the atypical behaviour of a particular vehicle, or the main character's inability to engage in melee combat and aptitude for getting stuck in the scenery), the experience isn't about to inexplicably turn sour.

It doesn't take long to realise the storyline really is far from sweet, though. All GTA games are based on stealing, smuggling, pimping and murdering your way up the criminal underworld, true, but they're done with a degree of wit that, combined with the game's stylised visuals, effectively points an Uzi right at the face of any moral objections and sends them cowering to the back of the mind.

It's not a psychological trick, just an ingenious way of packaging unsavoury content in a palatable manner. But in Vice City Stories, things are a little less appetising than usual.

Sure, there's still more wit in just one of the game's radio links between the glorious-as-ever licensed soundtrack than can be found in the entirety of the dialogue from many 'rival' titles, but there's now a harder edge and darker undercurrent to proceedings. And, odd as it may sound, that just doesn't sit well within the series.

Further diversion from the traditional GTA franchise recipe is evident in the quality of the narrative, which is considerably less engaging than previous GTA outings. (That's obviously of no concern when it comes to the two- to six-player ad hoc option: Ten modes are available, including deathmatch, race, capture the flag and territory-based type variants, and with skilled opponents they're a hoot.)

This time you're Vic Vance (brother of Lance, central character to the PlayStation 2 version of Vice City, which takes place in 1986, two years after the events of this game) who, after being stupid enough to get kicked out of the army, needs your help in order to build a criminal empire by taking over gang turfs and businesses within a seedy metropolis.

Typical GTA fare, then; the difference here is in the comparatively weaker characterisation and plotline. In addition, there's a noticeable slant towards shock – within the first hour of play, bestiality as well as spouse and child abuse are covered – and it costs the game some of its customary humour.

Why so much focus on the narrative? Because it's an integral part of the GTA experience. Yes, you're still offered a vast three-dimensional and impressively detailed playground of buildings, streets, pedestrians and police within which you're free to engage in as much lawless abandon as your mind can conceive. (See our PG Tips at the bottom of this review for some pointers – Ed).

And as ever there's huge amounts of fun to be had car-jacking the vehicle of your choice, cranking up the stereo and blasting through town, powersliding majestically around its 90-degree corners and mowing down civilians on its pavements while listening to some '80s classic with half of the Vice City PD on your exhaust. Or going for a quiet explorative drive in an attempt at finding all of the area's many, many secrets and opportunities for joyful mischief. Or jumping in a helicopter and surveying your empire from the skies while marvelling at the scale and gameplay content of the living, breathing city you hold between your hands. Even running a criminal empire through Vice City Stories' expanded business management options will be fun for some.

But, ultimately, without a little structure all of the above would soon lose its appeal. You need the direction provided by GTA's various missions that follow the many cut-scenes (book-ended by loading screens just long enough to prove annoying). It doesn't even matter that missions are little more than A-to-B-to-A affairs (and only a smidgeon more substantial than those of its predecessor), as long as the story does its job of bringing you into the GTA world.

That immersion is something Vice City Stories still manages, just, but its relative frailty serves as a further proof of how crucial it is to get all of the GTA ingredients right.

It's a bit like the Parisian patisserie using just the wrong amount of flour. Its cake is still delicious, and far, far better than the others available. But you can't help noticing there's something preventing it from matching in every way the maker's usual high standards.