In the handicam-hands of directors such as Paul Greengrass, the modern political thriller is all hurry and scurry: it skims rooftops, scuttles down side streets and scene-changes quicker than you can catch breath. Like life on a galloping horse, you never get to enjoy the view. In The Ghost, a political thriller from Roman Polanski, the film is slowed down till the viewing makes you uneasy.

Our hero is an unnamed ghost writer, played by Ewan McGregor, who spends his time, much like Leonardo Di Caprio did in Shutter Island, stuck on a Massachusetts island. McGregor's anxious and soft-spoken writer has taken what is supposed to be a straightforward assignment – one month to rewrite the memoirs of Adam Lang, the smooth former British prime minister played by the even smoother Pierce Brosnan. But the ghost writer ends up fearing for his life while caught in the middle of a vast plot: why really is the UK in the US's pocket? The politician is modeled on Tony Blair and his memoir is so hot, it's not allowed to leave the secured environs of the house. Neither, pretty much, is the film.

The Ghost, co-written by Robert Harris and based on his book, powers along with the solid if drab engineering of a taut thriller, drawing torque from international intrigue and a murder mystery. Polanski, as you would expect, crafts a mood of under siege. This is something he knows a lot about. He had to finish the film while under house arrest.

Our ghost writer is cooped up in the politician's modernist house in winter, surrounded by stern sea. He spends most of his day in the library where he tries to steal a digital copy of the book and iron shutters come down. In his bedroom, he discovers old photos of Lang that were hidden by a previous biographer, who died mysteriously at the start of the film. The dates in the pictures and the dates of his early political days do not match up. Adam Lang is not what he seems.

To the living room, then, where he dines with the former first lady Ruth (Olivia Williams), a fiendishly bright woman who riffs like Lady Macbeth. They go for walks on the beach, followed by tight security. When Adam is away on business with his assistant (Kim Cattrall), it's back to the bedroom where Ruth climbs into the ghost writer's bed. (McGregor's face, when he knows this woman gives him no choice, is exquisite.)

On Sky News, they watch Adam's old nemesis (read Robin Cook), who is now a UN envoy. He is pushing to have the former PM indicted for war crimes after evidence emerges he had a hand in the rendition of UK citizens to the CIA. The gates of the island house become mobbed by anti-war protestors and it doesn't take long before that famed Polanski claustrophobia starts to set in. "This place is Shangri La in reverse," the ghost writer moans. Not since Steve McQueen leapt free from the Nazis on a motorcycle in The Great Escape has there been a moment as potentially explosive as when our ghost writer goes into the shed and discovers a bicycle.

McGregor is an actor I usually don't believe in because he looks like a man who does not believe in himself. You sense a reluctance to dig deep. He acts as if he is afraid of what he will find. But his apprehension sits fine in the same room as Pierce Brosnan, an actor who believes intensely in the unruffleable, bland surface of brand Brosnan. There's not a shred of doubt in Adam Lang's eyes, not a moment where you sense the politician who wants to be liked.

For a while The Ghost looks like it is going to make something of Tony Blair, a cinematic citizen's arrest, perhaps. It gets up close and grabs him by the collar, then does a polite, uh, sorry to bother you. The plot then departs for la-la land, proposing the kind of corny CIA conspiracy beloved of the 1970s paranoid thriller. The film's twist – about the very nature of Britain's servile relationship with the US – is a silly mockery of real-life politics. The Ghost has grown-up pretentions but it lacks real mettle.

It seems unfair to mention Chinatown, Polanski's finest moment 36 years ago, and how that film kept its nerve and crackled with a startling cinematic brio. Here, Polanski is the ghost of his own film. There is a reminder of times past where he allows himself a moment of absurdity in the film's final scene, inspired by Kubrick's The Killers. But The Ghost never does seem to belong to him.

Steven Spielberg's contribution to the war film with Saving Private Ryan was to heighten the realism till it hurt. Glory was stripped away. Its only meaning was to ask, how do you survive in hell? In Lu Chuan's austere City of Life and Death, the Chinese director does something similar: he creates hell and makes it a fully lived-in experience.

Chuan's third film is a monument to the much-disputed Rape of Nanking – the 1937 massacre in which some 300,000 Chinese were killed by the Japanese Imperial Army. There is restrained Chinese nationalism at play here. I cannot imagine it will be a hit in Japan.

This is a melodrama-free zone, placing the war film on an arthouse canvas. It is shot with an unflinching eye in a crystalline black and white that fine-tunes the hard realism. The recreation of Nanking is a bomb-smoked marvel. You can taste its dust smoke in your lungs. Every frame resonates with life and death, survival pared down to the essentials.

The narrative follows soldiers from both sides and Chinese civilians trying to stay alive, from the initial sacking of the city to the abuses of its refugee camp. PoWs are slaughtered in their thousands. A beach becomes a sea of bodies. The refugee quarter is terrorised by lunatic soldiers. Rape camps are set up. Summary executions are rife. A child is thrown out a window. All the while Chuan contrasts this with clowning Japanese soldiers and just one of them with a conscience.

In one stunning shot, we witness soldiers looting, an execution squad at work and the marching of women off to a rape camp. Bodies swing from lampposts in the company of dangling decapitations. It is difficult, wearing viewing. The brutality dulls its poetry, its contrasting of inhumanity with moments of touching heroism. Chuan's interest is not in the mechanics of action, but in how it affects people. His camera is always alert to the human face. It is a terrible beauty.

Dear John, too, wants to show the downside of war. How sad that Channing Tatum's meathead special forces soldier and Amanda Seyfried's college student are kept apart by the war in Afghanistan. Stop the war! This pair are so boring and bland they deserve to be together. The story is set in the years after 9/11, back when the internet wasn't invented. We know this because they write to each other with pen and paper. But this middlebrow romantic drama from Lasse Hallström is not worth the paper it's written on.

Ricky Gervais's Cemetery Junction, co-written and co-directed with Stephen Merchant, doesn't ask much from you either. Let's see: a small-pond, blue-collar English town; a frustrated young insurance salesman Freddie (Christian Cooke); two pals who talk about leaving but are stuck-in-the-mud; and a gorgeous girl (Felicity Jones) who knows lots about Paris. You don't need a sat-nav to know where this is going. Sat-navs, of course, weren't around in the 1970s. Neither was political correctness. Gervais pops his head in as Freddie's working-class dad and lobs a few politically-incorrect smart bombs to liven the affair. But in his absence, this is a dull and predictable coming-of-age drama, much like the life it is hoping to escape.

The Daisy Chain, meanwhile, is an Irish chiller starring a heavily pregnant Samantha Morton. She acts like she doesn't want any trouble. This is set in the atmospheric, wind-blown west of Ireland where a dirt-faced girl called Daisy puts the heebie-jeebies up the superstitious locals. They think she's a fairy changeling. The way she stares at you, she could be auditioning for The Omen. Is she evil or misunderstood? Either way, an abnormal amount of people die mysteriously when she's around. Yet Morton's Martha thinks the child just needs love. Director Aisling Walsh (Song For a Raggy Boy) and writer Lauren Mackenzie aim for a higher IQ than standard horror. The Daisy Chain relies on the power of suggestion, pushing into the psychological. It creates some uneasy moments, but doesn't really come together.