Wouldn't Scooby Doo be more like the Oscar Meyer Bologna? It's mass-produced for a long time and made without any love, so yeah.
Futurama's revival took a lot shorter than Star Trek's, for what it's worth.
Stop saying "It only looks better because it's newer"! The average Tom and Jerry short from the '50s looks way better than any episode of Futurama. Futurama similarly looks way better than any Scooby series, both old and modern. Even older Hanna-Barbera shows like Yogi Bear and Huckleberry Hound, if not as well-animated as Futurama, are certainly much better looking than Scooby Doo and they were made just as cheaply.
Love or hate Spongebob, it was a creator-driven series made by people who loved what they were doing and had freedom to do whatever they want. I think that puts it on a slightly higher artistic plane than Scooby, which was made in the lows of the "cartoons are for kids; don't make them for your own enjoyment" era.
If Scooby can be called a "classic", it's due to fame rather than quality. And this isn't a list of the most famous cartoons, it's of people's favorites.