A good film basically is composed of certain variables. The main ones , arguably are : Script , Direction and Acting .

I haven't read Harry Potter books ( maybe the two first ones a few years back) , but as a human being , my instincts suggest that all the books are fairly of equal good writing and storytelling.

Story = Script : All Harry Potter films have more or less equally good script. ( the screenplay writer's work merely affects the actual story-script , written by J.K Rowling) Plus based on the fact that the main cast is the same , and the supporting cast of all films , although a bit different , clearly wasn't the attribute that resulted in the film's quality.

The attribute, that in the Harry Potter film franchise mostly affected the film's result is ( and cant be no other ) the direction.

The casted directors in all harry potter films are : Chris Columbus , Alfonso Cuaron , Mike Newell, and David Yates.

Out of those four directors , the best ones are : Alfonso Cuaron , Mike Newell ( check their filmography for proof).

The best Harry Potter films are the films directed by those two directors. The Prisoner of Azkaban and The goblet of fire.

Chris Columbus comes third best , and least skilled comes David Yates.

Ironically he is the one that was assigned to direct more Harry Potter films than all of the other directors . He directed the 5th , 6th , 7th part one , 7th part two ( coming).

The worst director the franchise ever hired , directs 4/8 of harry potter films. (The 6th one was the worst , totally neutral film , no impressions at all ) Harry Potter and the deathly Hallows is not a bad film . i give it a 7/10. What i am trying to state, is that if Alfonso Cuaron ( the best out of the four ) or Mike Newells had directed it, the result would have been much better ; it would have been a solid 8/10 ( i bet it would).

An example of David Yates mediocre direction is that in this 7th film , it was as if he didn't want to face " a hard to shoot- scene" .

The moving building , that appears first in the prisoner of Azkaban ( where a building appears in the middle of two other ones) , the part where the building slowly appears isn't shown on screen. we see two buildings , then the scene is cut , and then we jump the the scene where the third building is already there. As if he was bored to properly direct the film.

Mediocre direction + Good script + good acting = 7/10