The Harry Potter movies diverge significantly from the books, yet they are not devoid of merit.
The Harry Potter universe crafted by J.K. Rowling on paper is a timeless masterpiece, but that doesn't mean Warner Bros.' film adaptation lacks creativity or unworthy alterations. The movies have undergone numerous adaptations, some inferior to the novels while others are highly praised. Screen Rant compiled various opinions from Reddit users and selected details believed to be better than the novels from the Harry Potter film series.
Time travel
The third installment of Harry Potter introduced one of the most headache-inducing concepts in cinema - time travel. However, through easily understandable storytelling, utilizing both visuals and dialogue, the concept of time travel in the film Harry Potter and the Prisoner of Azkaban is considered much easier to grasp than when reading it in the books, not to mention the allure of intertwining present and past through the language of cinema.

The sacrifice of Hedwig
This scene represents one of the most acclaimed changes in the Harry Potter movies. In the books, Hedwig was accidentally killed by a Death Eater, missing its target Harry. However, in the film, Hedwig courageously flew out to shield Harry, sacrificing her life to protect her owner. Yet, Hedwig's death was later portrayed as a passing moment, not tormenting Harry as in the books, leaving fans disheartened.

Snape's Tale
Undoubtedly, Alan Rickman's performance elevated Severus Snape, restoring the character to the noble position he deserved in Harry Potter. Furthermore, Snape in the films possesses an incredibly captivating personality, starting with a cold, intimidating exterior and gradually becoming intriguing, sometimes even humorous, and ultimately filled with emotions. Additionally, the nuanced portrayal of the story between Snape, Lily, and Harry through his dialogues with Dumbledore is depicted with great finesse, eliciting sympathy for Snape even to this day.

Diagon Alley
Film serves as a bridge that contributes to bringing the audience's imagination of the world in the books to life. Diagon Alley in Harry Potter is one of the details wonderfully recreated and satisfyingly presented on screen, with even more intriguing advancements. For instance, the wall in the film can move and rearrange itself like a colorful puzzle, astonishing both Harry Potter and the audience rather than merely disappearing like air in the books.

Cedric's Demise
This scene is not only the most heartbreaking but also the most pivotal in the Harry Potter series of films. The interpretation of this scene on screen has left millions of viewers in tears due to its haunting portrayal, something even the books struggled to fully convey. Harry returns to Hogwarts with Cedric's body beside him, amidst the sound of trumpets and the cheers of the crowd. As each person realizes that something is amiss, Fleur's scream, Hagrid and Dumbledore's changing expressions, and ultimately Cedric's father's wailing cry. The climax is Harry's chilling declaration that 'Voldemort's back.' All of these elements combine to make one of the most emotionally impactful scenes for audiences in the early 2000s.
Ron and Cormac
Both male characters who crossed paths with Hermione during her adolescence are portrayed quite charmingly in the films. Despite significant alterations from the books, Rupert Grint's performance as Ron salvaged everything. Even the director of the third installment - Alfonso Cuarón - had to acknowledge that Rupert Grint embodied Ron after giving the actors a writing assignment about their characters, and Grint submitted a blank paper.

Similar to Ron, the mischievous Cormac McLaggen from the sixth installment is also depicted memorably despite limited screen time. Bearing resemblance to Malfoy, the film version cleverly turns Cormac into a more comedic character, leaving the audience with many laugh-out-loud moments while Malfoy is becoming more 'serious.'

Source: Screen Rant