I've always thought "Carnivale" had the most creative opening credits I've ever seen. The theme and visuals sold the show. Variety today raises a great article: what happened to TV theme songs? Ugly Betty is the shortest (12 seconds) and some shows basically forgo them altogether.
Whatever happened to TV theme music? - Entertainment News, Road to the Emmys: Creative Arts, Media - Variety
Whatever happened to TV theme music? - Entertainment News, Road to the Emmys: Creative Arts, Media - Variety