It’s always a bit of a struggle for Manhattan’s midtown architecture, clamouring to make itself heard above the braying advertisements that populate the side of every building. This is never more glaringly obvious than in the shining, pulsing heart of Times Square. Cadillac fins, rotating lobsters: the Art Deco pastiche layered upon kitsch layered upon neon is fun, but the architecture suffers.

Now that other cities — Shanghai, Beijing — are stealing its thunder as the city of the moment, New York has long been in danger of doing a Paris, content to grow old conservatively, mummified behind a polished mask from its grittier, more alive heyday.

This is a city created by property developers, but for the past 30 years it has rested on its laurels. Only now is it emerging from its coma — not in Ground Zero; they’ll be squabbling there for years to come — but in midtown, New York’s tacky heart. In 2002 Raimund Abraham’s totem-pole Austrian Cultural Forum (East 52nd Street, between Madison and Fifth Avenue) arrived from another planet.

Then, down the road, came Williams & Tsien’s American Folk Art Museum, with its bold Cor-Ten steel façade (West 53rd Street, between Fifth and Sixth Avenues). Last year Yoshio Taniguchi’s polished if passionless new MoMA reopened. All real, gutsy architecture. All cultural institutions, so more likely to take architectural risks than a commercial client, but still a sure sign of a more adventurous climate.

Some thank Mayor Bloomberg, who has been fast reorientating the city towards tourism, leisure and culture with more class than his predecessor by underwriting serious large-scale initiatives in which architectural quality is an economic generator, such as turning the High Line railway viaduct on the West Side into an urban promenade. Philip Nobel, a critic for Metropolis magazine, says: “The city is finally not fighting but facing up to the fact that it’s a playground, being honest about it, maybe even doing it well.”

The establishment left-fielders Diller & Scofidio won the High Line commission and are also renovating the Lincoln Centre. One of the city’s brightest young architectural firms, ShoP, has teamed up with Richard Rogers to win the East River Waterfront Park commission, a two-mile stretch at last opening Manhattan out to its best asset, its long-neglected waterfront.

But the most encouraging sign that Manhattan is cranking up the architecture is that the big corporations, the very people on whom this city is built, are now following suit. Even Donald Trump’s latest towers are more Mies than Vegas.

The standout success is the new Hearst Building. It’s a small skyscraper by Manhattan standards, just 40 storeys. But it peeps out on to Eighth Avenue between 56th and 57th Streets, pale, silvery, white, confident with its distinctive bevelled corners, but not belligerently so. It’s gentlemanly, courteous. An Englishman in New York.

This is Norman Foster’s American calling card, astonishingly the first proper American project for a man who seems to have converted the entire globe to steel and glass and subtle sleight of hand. Before Christmas Larry Silverstein, the leaseholder of Ground Zero, announced Foster as the architect of the third, 65-storey, skyscraper on the site, 200 Greenwich. Foster was presenting his design to Hearst’s CEO, Frank Bennack, when the World Trade Centre was hit.

Several weeks followed when the very notion of ever building another Manhattan skyscraper was in question. Meanwhile, Foster entered the Ground Zero competition (a finalist), some normality returned and Hearst announced the first major construction project in New York after September 11.

It was the right decision. This is the best new skyscraper in New York for decades, and one of Foster’s better buildings in his chequered recent past. The tower rises out of the stone shell of the HQ built by the Viennese architect Joseph Urban for the media tycoon William Randolph Hearst in 1928, back when architects knew how to do philanthropic civic kitsch (in a good way). As the base’s solidity and monumental fluted columns suggest, Hearst and Urban had planned a tower to rise above. It never came, and Hearst’s empire fractured into rented offices, which this building now unites in one.

Designing an extension, especially one larger than the original, is tough. Follow the original? Do something new? Choosing Foster, an old hand at the old and new game (sometimes successfully — the Reichstag — sometimes not — the British Museum’s Great Court), meant somewhere in between. Its basic shape, contoured by Manhattan’s age-old planning laws to allow light (though not taste) to the streets below, suits its context, but chooses to distance itself from the base with a back-lit, glass skirt, before shooting skywards in its Buckminster Fuller-inspired glass and steel diagrid (a diagonal grid of supporting bars), the kind Foster’s been playing with lately in his lifelong obsession with designing the ultimate, self-supporting, wraparound, shrinkwrapped façade.

This latest model is both structurally economic — it uses 20 per cent less steel than a conventional skyscraper and is quietly ground-breaking with its (by New York standards) high eco credentials — and fun, its facets catching the light beautifully. It’s just an old-school Modernist skyscraper, like Manhattan used to make, an efficient building expressing its structure nicely, without the insane kitsch of its near midtown neighbours. It does what it says on the tin. As Foster says, it’s “not iconic, but a building that simply speaks of its time”. And all without resorting to stick-on Caddy fins.