Beat me to it, Ink. Granted that it's a fantasy story with a simplified presentation of complex realities, the pivotal question becomes, "Has this person submitted his will to Aslan?" In the case of Jadis and Uncle Andrew, the answer is no, in the case of Frank, Helen, Polly, and Digory, the answer is yes.
Interestingly, the figures of Jadis and Uncle Andrew illustrate a point that Lewis makes elsewhere, borrowing from the classical tradition: that the greater a thing is by nature, the worse it is when it goes wrong. Uncle Andrew was unsubmitted, but he was weak. This made him cruel, petty, spiteful, and cowardly, but he wasn't nearly as great a danger as Jadis was. She was strong, determined, and assertive - things that are, of themselves, good. But the fact that they were unsubmitted to Aslan made them very dangerous, since she was using those strengths for herself rather than others. Imagine the strength and determination it took to run from Lantern Waste to the Hidden Garden, day and night, in order to get there before a flying horse could! One can understand why Uncle Andrew would admire the "pluck" of such a woman. It was his blindness to his own rebellion and ambition that made him blind to those attributes in Jadis.