Jan Fabre: L'Ange de la métamorphose, The Louvre, Paris<br />Figuration Narrative: Paris 1960-72, Grand Palais, Paris

A show that places Jan Fabre's work alongside the hellish imaginings of his fellow Belgian is a damp squib. Better to stroll down the boulevard

As a rule, interpolating contemporary artworks into Old Master collections strikes me as a bad idea, the outcome suggesting either that classicism needs justifying by its modernity or vice versa.

So Jan Fabre's L'Ange de la métamorphose at the Louvre is doubly worrying, first because it is set in the museum's wonderful Northern Schools gallery, and second because Fabre is a fine and oddly overlooked artist. That he is also Belgian makes your toes curl in anticipation, unhappily fulfilled by exhibition leaflets claiming Fabre as the inheritor of une tradition artistique flamande and comparing him with Hieronymus Bosch. The Louvre's first (and, to date, only) sally into crossover curating – a turkey called Counterpoint, in 2005 – was so viciously reviewed that you'd think it would have put them off. But no.

Actually, the worst that can be said of L'Ange de la métamorphose is that it is mostly possible to see it without being distracted by Bosch, or Bosch without being bothered by Fabre. The latter's Sanguis sum – a two-part sculpture of gilded lambs – obviously engages with Christian iconography: that one lamb wears a dunce's cap plays with the etymological link between "Christian" (chrétien) and "cretin" (crétin). Fabre's beetle-wing armour suits and self-portraits in blood are typically powerful, and hold their own among the glories of Bellechose. If that is the best that can be said of a show, though – that it is actually two shows that don't get in the way of each other – you slightly wonder what the point was.

Far better go to the Grand Palais, whose show Figuration Narrative ponders the last real moment when French art believed in itself. In 1964, the triumph of Pop Art was made official when Robert Rauschenberg won the painting prize at the Venice Biennale. Doubtless muttering intemperate words about Anglo-Saxon shallowness and inanity, a group of young Parisian artists rose up in arms and... well, did whatever they felt like, as is the French way.

(Very) loosely speaking, the group bound by the term "narrative figuration" rejected the pre-postmodern glibness of Pop and set about producing a painting of social engagement. Names such as Erro, Valerio Adami and Peter Stämpfli are mostly forgotten now, even in France. (Notably, most of the artists in the grouping weren't French.) Figuration Narrative suggests they should be remembered again, and quick.

It's hard to think why the painters in this show were sidelined by history, although an inconvenient lack of manifesto may have had something to do with it. Stämpfli's outsized car tyre, M301 (1970), puts him up there with Warhol, although he did not have the great good fortune to be born American. Gérard Fromanger's Boulevard des Italiens series (1971) has been scattered to the winds since its painting. Seeing it reassembled here, you despair that the Tate didn't have the gumption to buy it off the easel. As to the collective that produced Vivre et laisser mourir (1965) – an eight-part work depicting the collective's members killing Marcel Duchamp – where are they now? One canvas bears a wound where it was stabbed by an angry Duchampiste, although the work's subject visited the show and announced that he rather liked it.

Where did all this lead? For the most part, narrative figuration seems just to have petered out. Why is a mystery, this show being the freshest I've seen this year.

'Jan Fabre: L'Ange de la métamorphose', Louvre, Paris (00 33 1 40 20 57 60) to 7 July. 'Figuration Narrative: Paris 1960-72', Grand Palais, Paris (00 33 1 44 13 17 17) to 13 July