I write fantasy. For fantasy (and sci-fi), I think a great book stirs emotion. That's what's most important. The reader should care for the main character. Then an interesting and stirring plot comes next. If done well, the reader gets lost in the story. That's what I hope I offer my readers.
I feel like all writers believe their writing improves. So my first books were not as awesome as my newest releases (though I still hold fondness in my first ones). I've also transitioned genres to focus more on fantasy books from sci-fi.
My books have turned more personal now. They've always been character-driven, but most of my newer tales are written in first person. First person is a fun POV because writing as the main character allows me to be, not only a writer, but an actor too ;)