I agree with all you say Michael, and I would add that it's also the sheer elegance of her prose which captivates. I find it such a pleasure to revel in her style, which is restrained yet powerful. It's heartening to hear that she's still extremely popular with today's generation of readers.
Regarding Dickens, I lived, ate and slept in his novels from the age of about ten. I studied them for my A Level and at Uni. I was quite a 'buff' with quotes and knew every book inside out. But like Hardy, his style very suddenly ceased to please. Do you suppose that as we mature and grow, our literary 'needs' change? And yet, as I posted above, I still read Enid blessed Blyton!! Maybe I haven't grown up much after all!