Of all the pop people whom the British Isles have spawned in the last decade, only the former members of Take That could watch the show without hanging their heads in shame: the inventiveness, personality and perfectionism of the boys' extravaganzas were never challenged. Whereas Take That had years to hone their act in clubs around the country, the Spice Girls' first live performance was in a stadium in Istanbul last year. Whereas Take That learnt how to connect with their audience, the Girls just fling insults at each other as though they're halfway through a hen night - amusing for the length of a TV interview, but wearing when stretched over two hours. And Gary, Robbie and co would never have made do with that piddly little squirt of fireworks at the end.
Another field in which Take That reigned supreme was that of dancing, and the Girls have a lot of catching up to do: starting the show with a song called "If You Can't Dance" was not a prudent decision (as imprudent, in fact, as their movie slogan, "They Don't Just Sing!"). It can't be easy to trip the light fantastic in those stack-heeled trainers, but the Girls confine themselves to shuffling around and striking poses, delegating the Terpsichorean duties to six acrobatic hunks called, predictably enough, the Spice Boys. Even "Sporty" Mel C is still to top the backflip she performed way back in the video for "Wannabe".
On the other hand, the Girls' most obvious flaw has always been their singing, and here they were enormously better than expected. Even "Posh" Victoria could hold a tune, and "Baby" Emma turned in a creditable solo rendition of the Supremes' "Where Did Our Love Go" (chosen purely for how often the word "baby" crops up in the lyrics). When the Spiceworld comes to an end, she is guaranteed at least two Top 30 singles of her own before she settles into a career as a children's television presenter.
The prevailing view is that Mel C is the best singer, but that all depends on whether you think a window-rattling shriek is an asset or not. The Girls obviously think it is, because there is a terrible moment towards the end of every song when the other four sing the chorus in unison ("Stop right now, thank you very much ... ") and Mel C screeches the words to a different rhythm ("STOP - RIGHT - NOW!") over the top. Still, to give her her due, she is by far the most committed performer of the five, putting her every ounce of energy, and her every facial expression, into every song (I'm sure she's related to Eunice from Gladiators). And on "Viva Forever", when she harmonised with "Scary" Mel B, along with a Spanish guitar and a surging synthesised orchestra, I must admit I had a lump in my throat.
Which brings me to the music. I'd always viewed the Spice Girls' albums as having little more to offer than photographs of Mel B (particularly fetching on Tuesday night, perhaps because of a rare allergy that brings her out in a rash if she covers her upper body with anything more substantial than a Wonderbra). But at Manchester, most of the songs were distinctive, funky and vibrant, with a hard-rocking edge - and it'll be a good few years yet before we're able to sing along with this many All Saints tunes.
Who would have thought it? Dozens of outlandish theories have endeavoured to explain the Spice Girls phenomenon; it's weird to think that something as marginal as the music may have been behind it all along.
Speaking of weirdness, the concert's main strength and main weakness is just how perplexing it is. For instance, in the corner of the video screens is an insert of a man translating the lyrics into sign language, for those pop fans who are, well, deaf (he doesn't attempt the Spanish passage in "If You Can't Dance"). And the visuals never seem to have the slightest relevance to the songs they supplement. Why do the screens show an egg-timer engulfed in flames during "Walk of Life"? Why, on "Say You'll Be There", are the Girls twirling canes like Charlie Chaplin? And who dreamt up the staging concept for "Move Over"? The Girls strut down a catwalk in parodically ostentatious clothes - Victoria in an oversized boa, Geri in a cowboy hat. The Spice Boys, in trilbies and trench coats, are press photographers. There's a pretend catfight and Mel B is pushed off the catwalk; then one of the photographers is captured and stripped down to his underwear. (Then there's the interval: half an hour long, which is just enough time to show commercials for all the products the Girls have endorsed.)
It may seem like ill-thought-out nonsense, but I have a nagging suspicion that there were hidden layers to this gig. At the start, before the Girls emerged from their "Spicecraft", a voice-over paraphrased Star Trek: "Spice, the final frontier ... their mission, to boldly go where no woman has gone before." Before the encore, another voice intoned a line from a less likely source: Blade Runner. "The light that burns twice as bright burns half as long ... and you have burnt so very, very brightly." So, the Girls began the show with a utopian vision of the future, and finished it with a dystopian one, comparing themselves with Blade Runner's replicants: short-lived, laboratory-manufactured humanoids. Crumbs.
I'm not sure if I'm getting carried away here, but this would seem to be an unsettlingly stark metaphor for existence as a pop star. You can keep your Brian Enos and your Peter Gabriels. If it's postmodern intellectual stimulation you're after, go and see the Spice Girls.
Manchester Nynex Arena (0161 930 8000), tonight; Wembley Arena (0181 900 1234), Tues, Wed, Sat, Sun 19 Apr, 21, 22, 25 & 26 Apr; Birmingham NEC (0121 780 4133), 28, 29 Apr, 2, 3, 5 & 6 May.