I have watched the original Wizard of Oz numerous times; and it is a movie that has stood the test of time. I was intrigued by the concept of a prequel to the series but did not hold out any hope that it would be as good as the original.
The new movie does have a few things going for it. There are a lot of references to the older classic, and overall the story ties together - including how the wizard came to be in Oz (a balloon in a freak wind), to granting gifts and some of the contraptions that the supposed wizard will come to use in maintaining his mirage. It also has some fantastic visualisations of Oz, enhancing its fantastical nature.
That said, the script was very cheesy, and the movie felt like it dragged on for too long. While it is a perfectly entertaining movie, it is hardly one that will stand the test of time.