I love Scooby! I almost like it enough to enjoy the Scooby Doo live-action movies--almost.
What is it about Scooby? I enjoy the mix of different types of kids. I appreciate that the ghosts are never real. The kids always stick with the mystery and the danger until the case is solved. Every one of the gang shows bravery (some with more Scooby-snack prodding than others). There is some adventure because they are teenagers off on their own. Overall, the kids are heroes and the themes are reality-based.
What has been done with Scooby since Cartoon Network bought it is unfortunate in some ways. I think parents and kids who watch the recent movies (like 'Zombie Island') will see shows that promote other-worldliness and a lot of attempted one-up-manship within the team. The new Cartoon Network realization is unworthy of the orginal Scooby.
P.S. I am NOT counting Scrappy.