The biggest problem with the movies is that there is no real flow to the narrative and that they are merely a montage of 'best of' scenes.

Also, since the first movies were directed by Chris Colombus who was pretty well known for working with children and family orientated comedies.  So basically in the first 2 movies where you had Harry Potter and gang mimicking Macaulay Caulkin from the home alone movies.

While the movies do get progressively darker, in line with the books, they are limited by the cast who were selected based on their cuteness in the first movie.