In my opinion, basically the story is very good. Merlin has 3 apprentices: Balthazar, Horvath and Veronica. His enemy Morgana wants to raise dead sorcerers and rule the world. Morgana makes Horvath betrays Merlin and kills him, but with his last dying breath, Merlin gives his dragon ring to Balthazar and tells him that the ring will lead him to someone who will become a sorcerer as powerful as Merlin, someone who will destroy Morgana forever. Meanwhile, Morgana and Veronica are trapped in The Grimhold (a matryoshka doll/Russian nesting doll). Later, Horvath are trapped inside as well.
Centuries pass by and Balthazar is still looking for the person who is chosen by the dragon ring. He travels around the world and finally arrives in New York, where he meets young Dave. The dragon ring chooses Dave, who accidentally sets Horvath free from the Grimhold. Horvath now wants the Grimhold to set Morgana free, while Balthazar must guard it and teach his new apprentice so that he is prepared to fight Morgana.
Such a promising story is ruined by its main character: Dave. He talks too much (as often pointed by Balthazar and Horvath) and whines too much. Whoever wrote the dialogues must be thinking that they were funny; well, they are not. I hope Dave doesn't represent normal American boys. He is so irritating. The movie will be better if he is given less dialogues. Older generation played by Nicolas Cage, Alfred Molina, Monica Bellucci are sensible, intelligent, civil; but the young ones like Dave and Drake Stone are disappointing. Becky is okay.
There is a scene where Dave makes brooms clean the dirty floor for him, like Mickey Mouse in Fantasia. I haven't seen Fantasia for years, but I think the music used is the same. The end is the same: the whole room is flooded because Dave doesn't know how to stop the brooms, but thankfully the master arrives at the right moment.
Balthazar tries hard to teach Dave, but besides complaining and whining, Dave also cannot concentrate because his mind is full of Becky. It's typical of American movies, where love and family is more important than saving the world. When Morgana appears, suddenly Dave becomes powerful (he usually only makes small ball fires) and can defeat her, with a little help from modern science.