Hounds of Love is a classic and one of the very finest albums of the eighties.
She's never done anything as strong at any point in her career in my opinion.
http://rateyourmusic.com/artist/kate_bush
Pi (2005) was not a disappointment, but The Sensual World and The Dreaming are probably a bit better. Or you could always get The Whole Story or This Woman's Work vols 1 and 2.