GrandduchessElla provided a wonderful summary earlier in this topic thread.
Princess Cecilie was truly the "fairytale princess" of the early 20th century in Europe. Beautiful, generous, caring, loving, outgoing. The German people loved her as did peoples from other nations.
Given the long life that Wilhelm II had and the fact that Cecilie died relatively young, had she risen to level of Empress, her reign would have been brief and hence possibly without many accomplishments. Nonetheless, as crown princess, she is one of the most memorable, quintessential princess in history.