His books are entertaining, but "great"? Speaking as someone who suffered through Speaker and Xenocide and couldn't get past the first chapter or so of the first Thomas Covenant book, I beg to differ.
Card definitely has his own style with his work. Whether it's great or not is dependant on the reader - http://one-starreviews.tumblr.com/ gives some fantastic examples.
If you can, try the Seventh Son series though. easier read than Speaker or Xenocide, and very interesting IMO.