I've written a number of fantasies that I target as YA. Mainly because the characters are young teens. The Jewels of Earda series and the Henge Betrayed series are some of them. One thing I've decided is that fantasy when it doesn't involve heavy relationships is suitable for young adults.
Why does fantasy appeal to people. Imagination and magic. Dragons and elves. Ogres and fairies. So many strange and mystical creatures inhabit the pages of fantasies. So many of the stories we read as children have elements of fantasy in them. Fairy tales show worlds where things that we find unusual are normal there.
What are your favorite fantasy tales and your favorite writers? I find Mercedes Lackey writes fantasies that appeal to adults and young adults. They also address problems of children face growing up. Andre Norton is another though her books are also science fiction. The Witch World series is another. Harry Potter also lives in a world of fantasy. The Narnia Chronicles also hit on fantasy. And they are tales to be enjoyed by the young and the old.
Some of my friends write YA fantasy like Gloria Oliver and Kathy Sullivan. I'm blocking on the names of others but feel free to share ones you know.