"Where do we come from ... where are we going?" asks the eximious Norman Rosenthal, panjandrum of the Royal Academy, quoting Gauguin in his introduction to the catalogue of Charles Saatchi's newly formed collection of immediately contemporary American art. But "Wot's the good of Hanyfink?" ask I, echoing Albert Chevalier, Cockney songster, a question to which "Nuffink!" was his answer.

Nuffink is mine, too, alas. Here is painting in abundance, a scattering of sculpture too, by artists for the most part either side of 30, and it is all derivative, imitative, familiar and stale, young bloods wading in the ebb tide of postmodernism. Here, whatever within their lifetimes has been done before, they do again, less well - and if it was bad when it had no obvious precedent, it is now worse and stinks.

Here nothing is original. This revelation may, of course, be the honest intention of the exhibition. The sane man may reasonably argue that Saatchi - who has made shrewd choices in the past and has done alone much of what Serota and his many minions should have done, and failed - set out in the spirit of enquiry to see what in the visual arts has happened in America since 9/11; America, the once great engine of Abstract Expressionism and Super Pop.

Saatchi has done exactly that. A less generous man might have returned empty-handed, but would we have believed his declaration that he had found Nuffink? Would we not have obstinately persisted in the belief that in the land of Liberty the history of art must be, if not still galloping ahead, at least at a comfortable trot into the future?

Surely he should have found Sumpfink? But no, he did not. And so, with common sense and wild extravagance in equal measure, he has, to prove his point, shipped all these examples of Nuffink to the Royal Academy - and what better place for them? - American coals to Newcastle, so to speak.

The paintings are large for the sake of it, flaccid and flabby; half the size, a quarter, a tenth, a twentieth would suit them just as well. Indeed a sweep of red brushstrokes eight metres wide would be mightily improved as an eight-inch Howard Hodgkin.

They range in style and subject from the nit-picking obsession of the lunatic outsider to the blandly decorative, from tinkering with printed illustration (far better done by the Chapman brothers) to the monumental splash of colour with the momentary impact of the hoarding-from the minute description of a shrivelled old man's wrinkled penis to three metres square of collaged detritus.

We have seen it all before and it is no better than a final-year show in the Frayling School of Art at Ponders End.

. Tomorrow until 4 November (0870 8488484).