Oz the Great and Powerful is a fun movie not unworthy to be a successor-- as a prequel-- to the great MGM movie of 1939. It isn't as good as The Wizard of Oz, but what is?
The land of Oz is shown in more detail than it was in 1939, though the principals remain the citizens of Emerald City and the Munchkins, who are a little less juvenile and bratty.
The travelers along the yellow brick road include a bellhop monkey who is as well created as Gollum or Yoda (and a good deal more believable than either). The porcelain doll-- she's called the "China doll," but she's porcelain to me-- has a surprising lot of effective facial expressions.
The same cannot, perhaps, be said of James Franco as the potential wizard. He has only half a dozen facial expressions, and fear seems to be beyond his reach. But it's surprising how little difference the human characters make, none of whom exactly stand out.
The three witches-- Mila Kunis as the susceptible one, Rachel Weisz as the bad one, and Michelle Williams as the heroine-- are as restrained as Franco. Apparently, director Sam Raimi did not want to let his real people appear to be losing the competition for our attention, as people tend to do when on screen with animals, children or special effects. In The Wizard of Oz, Judy Garland was perhaps lucky in being the only undisguised human being in Oz until the Wizard appeared at the end. And, even so, she is not the character we remember most, except for her songs.
Just relax, and don't worry about whether some of Franco's devices would really work-- even in Oz.