I honestly can't say. Cuarón is my favorite director, but Yates comes soooo close, and he's really done a fantastic job with the last two movies. I can't pick one to do all of them :)

i think he is the best,and i also like Chris Clombus

I don't even know which of the movies they've made.

Sorry about that! *palms forehead* I should've remembered to do that. Sorry :) Well, it won't let me add it to the answers so I'll post it here:

C. Columbus: Sorcerer's/Philosopher's Stone and Chamber of Secrets
A. Cuarón: Prisoner of Azkaban
M. Newell: Goblet of Fire
D. Yates: Order of the Phoenix, Half-Blood Prince, and the two parts of Deathly Hallows

No problem, it's easy to forget! Prisoner of Azkaban and Order of the Phoenix are my faves. But all of them are amazing. My least favorite is Half-Blood Prince though i was a little disappointed.

he was the one director he kept it loyal to the books

Yates destroyed Potter movies :/

Definitely Alfonso he's genious

I agree with NimfaDora

or Alfonso

Chris Columbus. He did the first two movies, and they had the best Harry Potter feel. Like, they felt like a whole different world, they didn't just say "it's different, accept it." He created a real Harry Potter feel. I can't say the same about the others (especially for David Yates. Ugh, I can't stand him as a director, and I was soooooo upset with the Goblet of Fire, I want to scream. Alfonso is okay, but he didn't quite do it for me.)