In the movies’ version of March Madness, Sam Raimi turns out to be a much better Tim Burton than Bryan Singer. Unlike “Giant Slayer” Singer, Sam’s got a sense of humor. Taking on a prequel to the fairytale that frightened generations, Sam does scary. And does it well.

“Oz, the Great and Powerful,” is a winning back-engineering of the Oz fantasy, a “How the Wizard got to be Wonderful” romp that is a stunning update “The Wizard of Oz’s” effects, and the most gorgeous use of 3D since “Alice in Wonderland.”

Screenwriters Mitchell Kapner and David Lindsay-Abaire manage just enough whimsy to make the movie’s two hours pass without irritation. Raimi, having cut his teeth on horror and brought “Spider-Man” to life, was the right guy to make this emerald-tinted world pop off the 3D screen.

But the cast, plainly packed with second or third choices, lets it down. Is there anything in James Franco’s past that suggests larger-than-life, a fast-talking, womanizing con-man?

And the three witches – Theodora, Evanora and Glinda – are Bland, Blander and Blond Bland.

Oscar “Oz” Diggs is a magician who escapes the cut-rate Baum Bros. Circus in 1905 Kansas only to be swept, by tornado, to the Merry Olde Land of Oz. Where things aren’t merry.

The king is dead, and “the prophecy” says that only a great wizard can replace him. Plainly, the guy with the same name as the place is their man.

Intrigues? The witch Theodora (Mila Kunis, never prettier) is smitten with him, her sister Evanora (Rachel Weisz) is jealous. They want the wizard to rid Oz of the Great Menace, Glinda (Michelle Williams), which Oz, easily bribed, agrees to do.

Sidekick? That would be Finley, a flying monkey Oz saves, who then owes a “life debt” to the pretend-wizard. He’s amusingly voiced by Zach Braff.

Oz must trek and travel by bubble through the far corners of Oz and sort out who the real villain is and how to fight the hideous, 3D flying baboons who have supplanted the Flying Monkeys as the source of children’s nightmares.

Franco, as Oz, turns on the charm and oozes insincerity as he passes on what he’s learned, conning small town tent show audiences – “Lies, the stepping stones on the road to greatness.”

But the witches – an Oscar winner, an Oscar nominee and a Golden Globe nominee among them – haven’t the necessary vamp to make these conjurers sing. A trip to “Wicked” would have helped them all.

Even with the stunning production design — done by “Alice in Wonderland” Oscar winner Robert Stromberg — which starts our story in a black and white Kansas, and even with Danny Eflman’s playful score, this “Oz” starts to drag in under an hour.

You may miss the witches’ guards’ (Raimi crony Bruce Campbell is one) song – “Oooo weee oh.” As the “climactic battle” story arc of WAY too many filmed fairytales settles in, you may find yourself checking the time and asking, “Donde estan los Munchkins?”

But fear not. Uncle Sam knows what you want. And when he’s done giving a new generation of tykes frights about apes that fly in the night, he’ll cover it all. If it isn’t Oz without Dorothy and those Ruby Red Slippers, he’ll at least do justice to L. Frank Baum’s malleable wizarding world and give us an Oz worthy of our times.

(The cast “Oz, the Great and Powerful” ALMOST had)

(My James Franco interview is here).

MPAA Rating: PG for sequences of action and scary images, and brief mild language

Cast: James Franco, Mila Kunis, Rachel Weisz, Michelle Williams, Zach Braff

Credits: Directed by Sam Raimi, written by Mitchell Kapner and David Lindsay-Abaire, based on the L. Frank Baum “Oz” books. A Disney release.

Running time: 2:10