Unlike the Geneva motor show, Frankfurt isn’t an annual event – it alternates with Paris. But it’s the big one. A vast, sprawling mini-metropolis of a show, a temple to the German auto industry which powers the European market.

But the 2013 event came at a time of severe market decline. Five years of sliding volumes, sales down 6.7% in the first half of the year, and the mighty German market falling by over 8%. Meanwhile Spain’s decline is such that the Big Five has become a Big Four of just Germany, the UK, France and Italy. The region’s manufacturing base needs major surgery, with VW Group boss Martin Winterkorn saying in Frankfurt that 10 factories should be closed to relieve the industry’s chronic overcapacity, and none of his counterparts is under any illusion that weak lending and high unemployment mean recovery will be anything other than slow and long.

Yet Frankfurt 2013 was the most positive for years. OEMs like Nissan which didn’t attend two years ago were back. There was no single stand-out high-volume model launch – partly because these days there are so many niches – but you couldn’t move for new product. Concept cars were strewn like confetti. Cutting-edge technology oozed out of the products. The feeling was that the market has hit the bottom and there’s only one way to go from here, so let’s design and engineer our way out of this.

Renault, the company which has fallen hardest in the downturn, had no less than five concepts. You have to hand it to them – after the massive commitment to launching five battery-only EVs at the worst possible time it’s going on another product offensive. But a statement by the company that it’s aiming to get 60% of its business outside Europe is telling: it’s pinning hopes on emerging markets and the continuing growth of the Dacia budget brand.

Nevertheless, the strategy is in sharp contrast with Fiat Group, which is failing to invest in new product, and also, when you look closely, Volkswagen. VW Group has very nearly 25% of the European market – helped by the decline of Renault, PSA and Opel but with the VW brand alone now accounting for a larger share than other OEM group. Yet apart from the Golf and Up! its huge Frankfurt stand was filled with ageing product.

What was new was the showing of its first electric production vehicles, the e-Up! and e-Golf. Always one to enter new segments when the market has already been primed and with well-proven offerings, VW has come late to the party but with impact, talking of up to 40 electric or hybrid variants, 14 of which will arrive by next year.

Frankfurt marked the moment when EVs began to move seamlessly into the mainstream of the displays, with almost every manufacturer showing versions of existing models with electric powertrains of various sorts. EVs were part of the show’s fabric as soon as you entered the gates, BMW providing a fleet of i3s to shuttle press around the showground, a high-impact demonstration of the car doing what it does best – moving four adults around a confined, busy road space in swish, stylish silence, and here giving a glimpse of the megacity. Mercedes and Kia also provided hybrid shuttles but everyone wanted to ride in the i3, which says a lot about the fascination it holds. Elsewhere the production version of Tesla’s Model S, a car as remarkable the i3, was displayed on a stand as underwhelming as its technical prowess is astonishing. This is a landmark car presented and styled like a Mazda.

Porsche showed how it should be done with the $1.05m 918 Spyder and a Porsche Design recharging point but, back in the real world, Volvo displayed the world’s first diesel PHEV (plug-in hybrid) engine. Range Rover launched and began taking orders for diesel hybrid versions of both the Sport and flagship Vogue models, Mercedes had a PHEV version of the brand new S Class, and BMW revealed a prototype PHEV system in its new X5. The trend for hybrid technologies to be used for performance as well as efficiency and performance is very much on its way.

Toyota even showed a high-performance hybrid concept of its Yaris supermini, developing 420PS. But its core message was giving its entire stand over to hybrids as it rather belatedly tries to establish perceived ownership of hybrid technology leadership. Since it launched the first Prius it’s quietly – too quietly – sold 5.5m hybrids, resulting in savings of 37m tonnes of CO2 and 13bn litres of fuel. It’s now selling 1m hybrids a year and will launch 15 new hybrid models by 2015, so the stats will accelerate. The next three years should belong to Toyota.

The growth of the B-segment crossover is one of the key current trends in Europe, and it was moved onto a new level in Frankfurt by the introduction of the Mercedes GLA. Audi has inevitably already entered the segment with its something-for-everyone product strategy, and BMW has extended its X range down to a 1-Series model, but the Mercedes, with less of a scaled-down SUV shape, could be the most popular of all. This could conquest sales from the mainstream offerings of Peugeot, Renault and Opel, and to make their lives more difficult Lexus previewed its own crossover with a leftfield Darth-Vader-like concept. But the car which stole the Mercedes show at its massive hall was a concept S-Class coupe set to replace the CL next year. Even stripped of some of the chrome and detailing, the production version will be a must-have in Florida, LA, the Middle-East, Moscow and Shanghai.

BMW’s hall was demure by comparison. The production i8 electric supercar was there, albeit rather shyly presented, which is no bad thing. BMW likes to manage – and exceed – expectation, and no doubt it will with the i8. It’s no 918 Spyder, but then it will cost a mere $150,000, and in its own way it’s just as clever, with super-lightweight carbon and aluminium architecture, a futuristic body form, 100 mpg and the performance of an M3. Talking of which, the M3’s replacement, the M4 coupe, also debuted at Frankfurt.

BMW’s big rival Audi, for all its sales success, seems to be running into a designer’s equivalent of writer’s block. It trumpeted the Quattro concept, an homage to the original, groundbreaking Quattro of 30 years ago. Yet this looked very similar to – and not as well resolved as – a concept shown 2010. Its other Frankfurt concept, the Nanuk, was a total surprise and yet familiar. Anyone who was in Geneva earlier this year would have seen this, less some Audi detailing and minor styling changes, on the Italdesign Giugiaro stand as the Parcour concept. As an off-road supercar it’s interesting, but it should have been designed as an Audi from the start.

Where Audi has been hugely successful in recent years is in introducing premium products in lower market segments. Like Renault with its Initiale sub-brand, Ford is now attempting to go in the opposite direction by providing a premium experience for its mainstream models using the Vignale banner. The company showed a restyled Mondeo, a conventional product in the declining D segment, which under the Vignale name will give customers a dedicated dealer contact and concierge services. It’s a tough goal and Ford may well be better off letting the product do the talking– the S Max concept in Frankfurt is a compelling design and clearly close to production.

But perhaps the most significant show theme was platforms and specifically scalable and flexible architecture. In addition to the Renault-Nissan architecture showcased in the new Nissan X-Trail, PSA’s low-cost, low-weight platform underpins the vital new Peugeot 308 launched at Frankfurt. But the importance of platform strategy is underlined by being absolutely vital to the fortunes of two smaller companies – Jaguar Land Rover and Volvo.  Volvo’s star was the Concept Coupe, sitting on the next XC90’s platform, which has been designed to accommodate Volvo’s new family of four-cylinder-only engines and hybrid drivetrains announced in Frankfurt. Jaguar’s C-X17 concept, built on a new aluminium architecture, is a remarkably successful styling interpretation of the brand in an SUV form. It’s clearly intended for production, and Jaguar will be expecting a Cayenne-like uplift when it launches. But more importantly the same unerpinnings will give rise to a compact model family to compete with the BMW 3-Series off in 2015, transforming volumes and potentially changing the motor industry order: the C-X17 is not merely an SUV and the first iteration of a new architecture, but a disruptor, a catalyst to the change within Jaguar necessary for growth.

This may have been the most significant Frankfurt show for decades.