Frida Kahlo & Diego Rivera: Masterpieces from the Gelman Collection, Pallant House Gallery, Chichester

Seeing the work of Frida Kahlo and Diego Rivera hung side-by-side offers an intriguing insight into their fates

Fifty years ago, you would have been very likely to have heard of Diego Rivera, much less so to have heard of his wife.

Now, their rankings are reversed. Everyone knows who Frida Kahlo is, while Rivera, unarguably the better painter, languishes in her hirsute shadow. So, a show in Chichester that looks at their work side-by-side offers a chance to weigh the partners in Mexico's most famous art pairing against each other.

But first, a question. Why has Rivera been eclipsed by Kahlo? Well, he hasn't, really. The problem is that he was most famous as a muralist, so people usually only see his work in reproduction. Murals do not travel well. Equally, the politically engaged art for which Rivera is famous – he and Kahlo had Trotsky to stay in Mexico – does not hold up well in a day of schlock and sensation.

By contrast, his wife's work is right on the contemporary nail. Kahlo painted many things in her career, but mostly, and most memorably, she painted herself. For 26 years, from the age of 21 to her death at 47, she returned, again and again, to her own face. This was not the humanistic self-inspection of, say, a Rembrandt. Like the figures in a Mayan wall-painting, Kahlo depicts herself as a type rather than as a person.

In most of the self-portraits, she is expressionless and unchanging, a Mexican goddess with a single black eyebrow and faint moustache. She is Our Lady of the Sorrows, offering up her sufferings – polio as a child, multiple miscarriages, a leg mangled by a trolley bus – for our salvation. She is Our Lady of the Monkeys, of the Mayans, of the Revolution. In one late portrait, The Love Embrace of the Universe (1949), she is a godhead, complete with a baby Rivera as the Christ-child – a self-perpetuating myth, her own act of creation. All this put her in precisely the right place when American art historians discovered feminism and multiculturalism in the 1970s.

At her death in 1954, Kahlo was hardly known outside Mexico; it was Rivera who was given a one-man show in 1931 at New York's Museum of Modern Art. This, in his spouse's view, was only as it should be. Despite her many infidelities and a short-lived divorce from Rivera – they un-wed in 1939 and re-wed in 1940 – Kahlo was, in one regard, a good Mexican wife: unexpectedly self-effacing about her own genius, she was in no doubt at all about her husband's. One of the ironies of posterity is that her fame is based on a feminist misunderstanding of what she was. Her frank stare (and facial hair) give her an air of masculine authority that largely wasn't there. The other irony is that she would have been mortified at being more famous than Rivera.

She needn't have been. As the Pallant House show makes abundantly clear, Kahlo's art and Rivera's had relatively little to do with each other. His artistic stock has not gone down because hers has gone up. Despite their emotional and political closeness, Rivera was a more sophisticated painter than his wife. He had studied in Europe and embraced Cubism; she said that she would "rather sit on the floor of the market of Toluca and sell tortillas than have anything to do with those 'artistic' bitches of Paris".

Rivera, from an aristocratic colonial family, uses Mexico and Mexican-ness as a starting point for modernist experiment: his Calla Lily Vendors (1943) suggests, more than anything, an interest in Fernand Léger. Mexico, for the part-Indian Kahlo, was something altogether more visceral, as her husband recognised. "She is someone who tears open her heart and chest to tell the biological truth about what she feels," he said.

And that is the reason for Kahlo's post-mortem success. She is the progenitor of me-art, and of an art of morbid fascination. We see Kahlo through the wrong end of the historical telescope, inventing her backwards via contemporary artists whose work so strongly resembles hers. Her Chromophore, Auxochrome (1944) – an encoded portrait of herself and a lover – might have been made by Damien Hirst. Without Kahlo's Self-portrait with Bed (1937), there might have been no Louise Bourgeois, certainly no Tracey Emin. It was Kahlo who made the female psyche and sexuality possible subjects for art.

There are overlaps between Kahlo's work and Rivera's – an interest in hair, for example, his pubic, hers facial – but mostly they are on different missions, a truth this thoughtful exhibition acknowledges by showing them together but separately. A rare moment of collision comes with Kahlo's portrait of Rivera. Her father had a photographic studio, and Kahlo shows her famously frog-like husband in the familiar pose of a studio still. A portrait of the husband in the style of the father. What are we to make of that?

To 2 Oct (01243 774557)

Next Week:

Charles Darwent sees Michelangelo Pistoletto at the Serpentine

Art Choice

Nan Goldin's new show, Fireleap, sees a casual snapshot style applied to capturing children growing up – from pregnant bump to adolescent – at London's Sprovieri Gallery (till 6 Aug). At the other end of the spectrum, Devotion by Design, the National Gallery's exhibition of Renaissance altarpieces, shows rich examples of religious art (till 2 Oct).