Last Monday morning across Japan, thousands of disappointing little signs were being plastered over every electronics store in the country: “ kambai” - completely sold out. The feeding frenzy lasted just two days, but Nintendo had shifted its entire launch production run of 236,000 units of Wii Fit – a new “game” that threatens to bring vigorous physical exercise into that part of the home that used to be dedicated to a nice slump on the sofa.

For the past three years, Nintendo has made something of a habit of this. The Japanese company may be the darling of investors, but for the rest of the world it has made December a month of improbably long queues, disproportionate anticipation and – for most would-be customers – unbearable frustration.

The big question is whether those brisk sales of Wii Fit in Japan justify Nintendo’s present market capitalisation of more than £43 billion. After all, Wii Fit is selling the entire package – the balance board that registers your every exertion and the game itself – for a little under £45 and it is not even going to launch in the United States or Britain until next year. Even if Nintendo sells a Wii Fit game for every one of the 13.2 million Wiis it has sold worldwide, that represents less than £600 million in sales.

In November, Sony’s PlayStation 3 outsold the Wii in Japan – a triumph that has not yet affected Wii’s exuberant shares but has left a few investors with vertigo only weeks from the end of the calendar year. The optimism for Nintendo lies in two beliefs. The first is that the Wii, unlike the PlayStation 3, is priced cheaply for a post-sub-prime market. For a US and UK shopping season likely to be the most cost-conscious in a decade, the difference between a $400 PS3 and a $250 Wii could easily clinch it in Nintendo’s favour.

But also there is a faith that the Wii will do more than any previous games console – it will saturate in the same way that television saturated the world’s living rooms.

Every year, one toymaker or another becomes the bane of parents because they cannot meet seasonal demand for their must-have product and customers dread the inevitable tantrums waiting for them at home. In only a year, Nintendo has created a completely different dynamic: most of the people in the queues for the Wii Fit were adults buying it for themselves. Their disappointment did not lie in the fear of miserable kids but in the fact that they may have to wait a while longer before achieving that ideal body mass index.

It is the people in those queues – the near 50-50 gender split, the astonishing speed of their conversion into gaming zealots and their adult-sized wallets – that so excite the investors. In the year since the Nintendo Wii was launched, analyst after analyst has made the shares his top “buy” of the year. With few other “sexy” stock stories on the moribund Tokyo Stock Exchange to set the pace, Nintendo has led an often lonely rally.

Since January, the shares have soared nearly 140 per cent. The Kyoto-based company briefly became Japan’s third-most valuable corporation – and all based on the assumption that the Wii can do to video games what the iPod did to music. Where the Sony PlayStation 3 and Microsoft Xbox 360 have opted for hefty graphics and serious gaming, Nintendo has opted for accessibility, family fun and, perhaps most significantly, a platform on which third-party game developers can try out some quirky new ideas.

Even Sony, which grew used to dominating the games scene with Playstation, has recognised the appetite for a new approach. On arriving in his new post as president of Sony Computer Entertainment, Kaz Hirai is said to have despaired at the long faces of the staff. “We’re supposed to be a company that sells fun,” he told them.

Nintendo’s portable DS games machine has been even better than the Wii at this new approach to games software. This year’s Christmas lineup of titles in Japan includes a guide to wine-tasting, Tarot readings, a teach-yourself Chinese class and a pocket yoga instructor.

Atul Goyal, an analyst for CLSA, says Nintendo has shown “a unique ability to understand what customers want. The management team understands there is no upside in forcing customers to use a manual.”

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