Whenever I listen to the Chopin preludes I like to listen to all 24 of them in order. They are very connective and cohesive as a set. That being said my favorites (at the moment) are no. 8, 13, 15, and 17. They change from time to time and sound different depending on who's playing them. Alfred Cortot is my favorite interpreter of the preludes. His playing is so deep, mysterious, and embodies the soul of Chopin for me.