The Whitcoulls top 100 list was announced a few days ago. It makes interesting reading from a SF genre point of view. There are a lot more genre titles than the previous year with a lot of them could be considered YA reading. Some authors of note J.R.R. Tolkein (twice), J.K. Rowling (four times), Philip Pullman, John Marsden, Audrey Niffenegger, C.S. lewis, Raymond E. Feist, Jean M. Auel, Joanne Harris, Paulo Coelho, Frank Herbert, Elizabeth Knox could all be accused of writing speculative fiction even if a few of them would not agree. That is quite a lot really and I may have missed some.
Remember that this is a popular vote and therefore has little connection with how good the book is - witness The Da Vinci Code at number 1. But it does show how entrenched genre fiction is within the general reading public - it does not just belong to the fan community.