Don't feel bad about not having a favorite book. Having a "favorite" so often means we make a competition between things we love. Why would you want to compare, because you'll just end up picking apart tiny negatives, destroying what you previously held precious. If you have a favorite, I think it happens naturally. Either a book that resonates fully with your being or one that had or continues to have a strong effect on your life.
My favorite book for a long time was The Horse and His Boy. It was a story that I loved for the shape of it.
I loved everything about the journey, the horses, the moonshadows on the beach as the lions chase the children together. It was one of the first books I approached critically. I've listed it as my favorite likely since I first read it when I was... say, 7? The entire Chronicles of Narnia were incredibly important to me and helped me form my moral code.
The Horse and His Boy was the standalone that I could be a bit reductionist about, that also encapsulated everything else I loved bout Narnia.
I read The Golden Compass and that, along with the rest of the series, really solidified many of my fundamental beliefs about the world, about my role in it, about how we should treat eachother, the pursuit of knowledge, etc etc. Its RIGHT THERE next to The horse and his boy, as far as favorites go. I even wrote my master's dissertation on Lyra and Will as savior figures. Those books shaped my life more than any other, in all likelihood.
And I'm reading the name of the wind for the 3rd time. Thats a lie. I finished it last night. Now i'm on the wise man's fear. And i think I have to bump those childhood favorites down a peg. Because every word that is written in these books feels like it was written for me. It hasn't effected my life in a tangible way, but it speaks things that I wish I could put into words. I get giddy about single phrases. I react to a situation in the book, and then the very next line is another character having the exact same reaction. If books were soulmates, this would be one of mine.
There's been books i've fallen head over heels for, that i recommend and reread and respect and adore. Persuasion. Caddie Woodlawn. The Juniper series i read when I was becoming a young woman, Ender and Speaker for the Dead when I was moving overseas. A Monster Calls. But Narnia and HDM formed a part of me at a Core Memory level- think Inside Out :P. Kingkiller Chronicles fit somewhere different. Rothfuss's writing hasn't changed my identity or helped me shape my life. Its more like resting my head on my own pillow after a long stretch of travel. It feels completely mine, like home, like a part of me. And that, I think, is something rare. Whether you find it in a book, a bit of music, a piece of art...
I don't have a favorite movie. Maybe you do?