A decade too old to convincingly be called “boy,” Sam “Mr. Greenscreen” Worthington is badly cast as reluctant-demigod Perseus—as was Harry Hamlin in the ’81 Clash of the Titans—but the appeal of sumptuous blockbuster Hellenism remains with the Gods (Liam Neeson as Zeus, Ralph Fiennes as Hades) and their miracles (3-D CGI replacing analog). This Clash provides frequent occasion for awe as Perseus and company, men in rebellion against the tyranny of Olympus, embark on a tour of hodgepodge theme-park antiquity, rendered in button-by-button detail: I especially liked the warped ferry to Hades, with oarsman Charon replaced by an outboard motor. Transporter director Louis Leterrier is sure-footed when battling Gorgons and giant scorpions, but he muddles the comic-grotesque opportunity of the Stygian Witches. His shopworn “hearty camaraderie” scenes and LOTR helicopter sweeps over exotic terrain don’t do much to sway one to the cause of humanity, and the hasty romance will make no heart palpitate. It’s not surprising to learn that Clash was converted to 3-D as an afterthought; nothing onscreen justifies wearing dumb glasses—until a certifiably stunning climax which has you barnstorming, on the back of Pegasus, above and through the streets of a Kraken-besieged city.