One of the first paintings you see as you enter the Gerhard Richter retrospective at the Museum of Modern Art in New York is a portrait of the artist’s uncle Rudi dressed in his Nazi uniform. The painting is from a family photograph of Rudi taken shortly before he went off to fight for the Wehrmacht. He was killed within a few days of leaving home in the autumn of 1939. In the portrait, it’s as if Rudi has already died and Richter is painting his ghost: the young man stands in front of what appears to be a crumbling wall, his facial expression not so much of indestructible optimism as of amused distraction, as he fades before your eyes into the greyness of the background, at the edge of non-existence. There is nothing heroic in Rudi’s posture - he’s merely an ordinary boy preparing to fulfil his patriotic duty. But already the light is failing, twilight is upon us, and Rudi is soon to disappear altogether, becoming no more than a construct of memory, both outside time and time’s victim.

Uncle Rudi (1965) is shown in the same room as Richter’s paintings of allied warplanes (Bombers, 1963; Mustang Squadron, 1964): grainy, obsessively detailed black-and-white images of these ambivalent machines of death that brought a terrible liberation to Germany. Born in Dresden in February 1932, Richter was a member of the Hitler Youth, and recalls hearing from a distance the bombs falling on his home city. He grew up in the old GDR during a period of profound silence and mourning in Germany, both east and west. Like the late W G Sebald, Richter remembers wandering as a youth through a purgatorial landscape of bombed-out and ruined cities, where so little was spoken and understood about the catastrophe that had unfolded in the German Reich. The Germans were, Sebald wrote, wilfully blind: when they turned to take a backward view, particularly of the years 1930 to 1950, they were always both “looking and looking away”.

Over more than four decades, Richter has assembled what he calls his Atlas, a huge archive of photographs. Some of these were clipped from newspapers and magazines, while others were taken by him: his defence in a personal war against forgetting. They are the inspiration behind many of his most memorable paintings, the subject of which is often perception itself, the act of both looking and looking away. Through the distortion of photographic representation, Richter attempts to show how the eye can both illuminate and deceive. The past, he seems to be saying, is unstable. The image, photographic or otherwise, is always artificial. There is no truth, only interpretations, which applies as much to our own personal narratives as it does to the hauntedness of the German past.

Richter escaped from East Germany in 1961, before the Wall was built, settling in Dusseldorf, where he attended the local art academy and became interested in the avant-garde, in particular in abstract expressionism. His early paintings were experiments in socialist-realist fantasy and, as such, have been excluded from this retrospective, though it would have been fascinating to evaluate them against his subsequent work.

In the late 1980s, Richter began a cycle of paintings about the Baader-Meinhof group, October 18, 1977 (1988), the student radicals whose early idealism and disgust at their own country curdled into nihilism. Richter professes to be sceptical of all ideology and dogma. One believes that he is sincere when he says this. And yet, looking at his paintings of the leading members of the gang - Andreas Baader, Gudrun Ensslin and Ulrike Meinhof - emaciated and exhausted by their trials in prison, one is moved by how their portraits are suffused with a sense of grandeur and loss. In particular, there are three startling portraits of Gudrun Ensslin as she is being returned to her cell (Confrontation 1, 2 and 3), adapted from police photographs and all softly lit. In the first painting, she turns to embrace the camera, smiling slightly: she is thin and ragged, her dark hair falls limply, and yet the light of a perverse idealism still shines in her eyes. In the second painting, she turns away from the camera, a young woman who, like Uncle Rudi, is in the process of being destroyed by the inexorable forces of history. In the third and final painting, she hangs her head in defeat: she is on the way back to her cell now, and to an ambiguous death.

In his introduction to the retrospective, Robert Storr, a senior curator at New York’s MoMA, suggests that although Richter had no sympathy with the revolutionary leftism of the student radicals, he regarded their “flawed, desperate and inevitably doomed idealism as a tragedy in the context of a society where human values were so distorted by conformity and the hope of fundamental change so remote”. But that is too neat. There’s both a harsh, unforgiving realism as well as an elegiac quality to the Baader-Meinhof cycle that, as with much of Richter’s work, defy the simple generalisation with which Storr seeks, again and again, to explain and entrap the German artist.

How good is Gerhard Richter? Well, it’s hard not to be impressed by his versatility and daring. There’s no one characteristic Richter style, no one programmatic aesthetic of representation. Walking through the huge open spaces of this exhibition, you are constantly startled by his choice of subject and style across more than 180 canvases, from realistic portraits and still lifes to abstract expressionism, pop art, and even Mondrian-like experiments with geometry and colour. It’s as if Richter, through his long career, has been continually pushing at the limits of his own versatility: how good am I? What can’t I do? What is, if anything, my natural style?

Michael Kimmelman, in a recent profile of the artist in the New York Times Magazine, went so far as to claim that Richter was the saviour of painting. One understands the anxiety that led him to make such a hyperbolic claim: admirers of painting, of brush strokes on canvas, are disturbed by the huge popularity and influence of conceptual art. But the death of painting, like that of the novel, is greatly exaggerated. There’s no such thing as Painting; there are only painters, good and bad. And Richter is a very good painter, if not quite a great one.

I prefer his earlier, less obviously virtuosic work, before he began experimenting too lavishly with colour, before his paintings were being sold for millions of dollars and great claims and counter-claims were being made for his work; most recently, Jed Perl, art critic of the New Republic, denounced Richter as a “bullshit artist masquerading as a painter”.

The portrait of Uncle Rudi and others like it painted in the mid-to-late 1960s - such as Stag and Motor Boat - with their smudged, restrained and washed out colours, are authentically strange and melancholy, befitting the strangeness of postwar Germany itself: a country at once in search of and in flight from history.