Magical Realism, Fantasy, Adventure
Technically speaking, the Harry Potter stories are a form of magical realism, since they ostensibly take place in our world. But given the whole "magic castles full of monsters and evil spell-slingers trying to take over the world" thing, the ordinary world takes a back seat to fantasy.
J. K. Rowling drew inspiration for the book from the great fantasy novels of English literature, particularly J.R.R. Tolkien and C.S. Lewis. But she also drew from Roald Dahl, whose works of fantasy were also largely set in the real world.
You can see similarities not only in the elves and trolls, but in things like the Dursleys, who make as convincing a set of wicked stepparents as you're likely to see. Harry's world also contains such elements as a great evil to destroy (lookin' at you, Voldemort), magic items to uncover and a hero on whom everyone is depending. That puts this film pretty clearly in Team Fantasy.
But the bulk of Harry Potter and the Sorcerer's Stone is actually a story of exploration: Harry spends a lot of time learning about all the nooks and crannies of his new world, rather than following a specific plot to its logical conclusion. This mirrors classic adventure stories (like Robinson Crusoe), whose heroes spend as much time acclimating to their new environment as they do solving mysteries or pursuing evil-doers.