The Bourne Legacy, Tony Gilroy, 135 mins (12A) Ai Weiwei: Never Sorry, Alison Klayman, 90 mins, (15)

When the actor Mark McManus died, no one thought his TV show Taggart could possibly continue, since there wasn't a Taggart any more. In fact, the series continued for years, on the understanding that any gritty-faced Scottish copper who could growl, "there's been a mrrdrrr" was essentially Taggarting, in a generic way. The same has happened with the Bourne series. Instead of recasting Jason Bourne after Matt Damon's departure, the producers have kept the title and put a new hero into the Bourne position. It's now Jeremy Renner Taggarting away like crazy.

When the Bourne trilogy hit its stride, much significance was attributed to the hero's initials. This was the tougher, no-frills new J B in town – move over James Bond. It's hard to put the Bond comparison aside in The Bourne Legacy, for one striking reason. It must be strange for female lead Rachel Weisz to star alongside someone who looks so uncannily like her husband, Daniel Craig – although Renner is more like a squidged-up, pop-eyed rubber bath-toy version.

The third Damon episode, The Bourne Ultimatum, was kinetically thrilling stuff, director Paul Greengrass infusing the action genre with the realist urgency of his docu-drama background. The Bourne Legacy is directed by Tony Gilroy, who wrote the three previous episodes and directed the terrifically intelligent corporate thriller Michael Clayton. But here Gilroy's wit deserts him.

Legacy starts confusingly. There are solemn, scowling meetings between stone-faced intelligence suits (Edward Norton, Stacy Keach, Scott Glenn), there are mysterious nosebleed incidents in Karachi and Seoul, there's lots of opaque talk: people babble about Treadstone, Larx and Emerald Lake and say such things as "State two plus 30 to splash" and more technical stuff besides.

Meanwhile, a man named Aaron Cross (Renner) is braving the Canadian mountains solo – swimming in icy water, swinging from trees, fighting wolves single-handed, getting his beard all frosted up, basically being Wolverine from X-Men. What we like best about him is that he doesn't say very much – although when he does, it's as inscrutable as the rest: "I dropped my programme kit. I'm out of blue in 32 hours."

The plot isn't nearly as complex as it first looks. Cross is, like Bourne, a super-soldier enhanced by the authorities in another secret programme. The powers that be, led by Norton, have shut down the programmes and want to eliminate Cross and his ilk. Cross has to keep taking his pills, one green and one blue, although it turns out he doesn't need the greens any more, because "they viralled everyone off greens five months ago" – still with me? So he goes to Manila to get his pills, in the company of Weisz as geneticist Dr Shearing. She's also in mortal danger, and relieves the tension by shouting a lot and being excitedly boffinish ("It's an incredible breakthrough in viral receptor mapping!").

Gilroy can bash out such stuff by the ream, which makes The Bourne Legacy seem terribly profound and intricate – only it's not. The narrative complexity of TV series such as Homeland and The Killing is something that blockbusters are desperate to muscle in on, but given only two hours' screen time, much of it to be filled with punches and explosions, the default way to simulate complexity is to fill space with technical chatter. Where Ultimatum worked both as high action and taut narrative, The Bourne Legacy clutters itself up with pseudo-complexity. We have to wait a long time for the showcase sequences, although they're good when they come: a genuinely scary lab massacre, an unexpected shootout in Shearing's house, a wham-bam climactic bike chase through the streets of Manila (in which, of course, thousands of Filipinos feature merely as stooges for Cross to shove out of the way).

While Weisz brings a human touch, Renner lacks the everyday vulnerability that made Damon so engaging. He's just another taciturn tough with an inexpressive scowl, although he's rather convincing shinning up buildings like Peter Parker. But the new Bond? He's George Lazenby at best.

Sometimes a documentary can be a great film, sometimes you just have to settle for it telling a great story – and Ai Weiwei: Never Sorry certainly scores as contemporary reportage. Alison Klayman offers us a portrait of the Chinese conceptual artist, dissident and indefatigable Tweeter, resulting in a more than serviceable primer on why Ai is an exemplary case of the artist as committed activist. There's good background material on Ai's days on the 1980s New York downtown scene, while the contemporary footage shows Ai being quietly, affably defiant towards the authorities who never cease to persecute him. A terrific scene has anxious police filming Ai (while they are filmed by Ai's videographer) and fussing around a dinner that the artist is having with friends and followers, a meal that itself represents an act of defiance.

The film offers a sobering insight into what it means to be an artist and a dissident in a country such as China (where even an earthquake's death toll is a state secret). It's less illuminating on the specific nature and meanings of Ai's art. Still, Klayman gets close to the man and, above all, to his continuing troubles. This is a functional, self-effacing documentary that does its work – it makes you aware of the significance and the courage of Ai, and of his less celebrated dissident peers. It's required viewing for those countless Western artists who routinely puff themselves as "subversive"; Ai Weiwei, like Pussy Riot, reminds us what that really means.

Up-and-coming US indie queen Brit Marling stars in and co-writes Sound of My Voice, Zal Batmanglij's oddball drama, in which she plays a cult leader (possibly) from the future …. Hitchcock fever continues with the restored silent classic The Lodger, in which 1920s croon idol Ivor Novello lurks with intent in the London fog.