The plot is pure choose-your-own-adventure: A bullied wuxia fanboy from South Boston (Michael Angarano) is teleported back into a LARP fantasia of feudal China, where he’s singled out as the long-anticipated “Chosen One” prophesied to topple the despotic warlord. Our nominal hero then recedes behind the two Mr. Miyagis who adopt him: a Lisa Bonet–bewigged Jackie Chan and warrior-monk Jet Li (English line readings: 75 percent intelligible). This is the first collaboration between kung fu’s Astaire and Kelly, and, as that, it disappoints. Like so much here, the fight arrangements by choreographer Yuen Woo-ping aren’t so much bad as undistinguished: The camera placement is off, the tempo unvaried, and Chan’s movements are obscured by his piled-on robes. The cinematography lacks storybook indelibility; Collin Chou’s Jade Emperor is a stock archvillain (though Li Bingbing’s bullwhip-toting “White Haired Demoness,” announced with apocalyptic reverb, is lovely) . . . and then there’s the scene where Li actually pisses in Chan’s face—a degradation familiar to viewers incensed by the demographic-outreach casting of white-dude Angarano. Taken as a whole, though, it’s an amiable lost-and-found of epic-adventure tropes. As I still illogically treasure Willow, many a 10-year-old who sees Forbidden Kingdom will remember it fondly in spite of its flaws.