Sometimes an exhibition changes the story of art. It rewrites decades of headlines and reveals a reality that had somehow been ignored.  The brilliance of Lucian Freud was not exactly a secret before this ruthless painter's death in 2011 at the age of 88. He was feted as an old master in his lifetime, applauded and honoured throughout the art-loving world. But by some sleight of hand, critics and art dealers from the early 1990s onwards pretended (for convenience's sake) that Freud could be bundled off into a corner, doing his painterly thing, while the Big Important Story of modern British art was happening in the Turner prize and Damien Hirst's wallet.  This stupendous exhibition changed all that. It made it pitilessly clear that all along, the only artist who really mattered in contemporary Britain was Freud. He was, and is, a titan whose works will be remembered when everything being touted right now as exciting art is forgotten.  In a way, an exhibition of Freud's portraits has a redundancy in its title – apart from a few captivating cityscapes and garden paintings, almost everything he ever did was a portrait. This show contained naked portraits, colossal portraits, head-and-shoulders portraits. Leigh Bowery loomed; Sue Tilley sprawled. The art critic Martin Gayford looked dashing. Freud's portrait of Gayford, the only painting by Freud whose creation has been described in a book by the sitter, is proof (if proof were needed) that Freud could be tender and friendly in the way he painted people – the image of him as a cruel observer is a cliche.  Not cruelty, but a raw appetite for life is what came through in this selection of a truly great artist's works. "Keep your eye clear / as the bleb of the icicle", says Seamus Heaney in his poem North. Lucian Freud did that, but if his art has an icy hauteur, its lucidity is grandly compassionate for humanity. The authority of the paintings in this exhibition put Freud in the company of his artistic heroes – the likes of Titian and Annibale Carracci. Soon, the biographies will reveal what is reputed to have been a startling life. But trivial gossip dims beside the genius to which this exhibition paid righteous homage.
Forget the story of British art you've been missold – no one matters more than Freud, as this extraordinary retrospective of the raw, tender painter revealed, writes Jonathan Jones