From the outside Buffy and Angel look completely lame but the way Whedon created and developed the characters and through them revamped all the old horror film staples while at the same time parodying all the dreadful 80s teen shows was excellent. To maintain that over more than 200 hours of TV while never dropping the quality or humour was miraculous and was something most directors couldn't manage.
Just watchig Firefly for the first time at the moment and he's managed the same thing in a different genre, why the pillocks at Fox canned it mid series is beyond me. George Lucas should have got Joss Whedon on board to do the character development and dialogue on the new Star Wars films, Christ Whedon managed to make Buzz and Woody seem human in his directorial debut while the supposedly fantastic Lucas managed to make Alec Guinness, Harrison Ford, Samuel L Jackson, Liam Neeson and Ewen McGregor seem wooden.