If blu-ray was a hot female, I'd be making love to it. XD
Unfortunately however, the change over to blu-ray is a slow process, so movies/shows that I wish were on blu-ray are not, just yet (especially imports like anime).
Needless to say, the cool thing about blu-ray is BD-Live. You can access more content with it, and even upload your own commentaries where others can watch/listen to you whilst watching the film.
Not only that, you have the chance to have a live commentary with cast and or crew, such as my experience with watching The Dark Knight with Christopher Nolan. There, we got to ask him questions, to which he answered. He also answered one of my own questions.