Foundation has all of the interesting concepts from the books, and adds a few of its own, also very interesting. The storytelling model is also very interesting. The world-building and epic plotline is captivating.
But the visuals, by Seldon's beard, the visuals. Every scene is like a painting, not the kind of painting that has broad strokes, but the kind where every little bit has an obsessive level of detail and little surprises.
I'm watching it for story now, and may go back and watch it again, slower, just to admire the spectacle of every scene.