Supernatural always seems to me to be nothing more than an attempt to get people in their late teens and early twenties to write more slash fiction. I much prefer Kolchak: the Night Stalker, which had no romantic elements. The more modern versions: The X-Files, Haven, and Sleepy Hollow all seem to include a romantic interest. Constantine, so far has not.

As far as the books, the only series I've delved into is the Dresden Files, and I don't see much character development in the title character, but a lot of the characters around him change as the series progresses.