[user104658]

The best films are the first two, they captured the "magic" in ways the rest didn't.

The best written books are Goblet of Fire and Half Blood Prince.

And honorable mention to the Deathly Hallows films - simply for being OK films when the book was a horrible mess. Though I put that down to the fact that I think she was writing the book with the movie in mind, by that point, so the book read like a confusing screenplay but translated easily to movie form.