Why is she

Well, her facial structure is just about as perfect as is physically possible. When you actually study the biological basis for why we find certain traits attractive, you can go down the list and see that Christina has an extreme example of just about ALL of the traits. She has very large eyes, a very small nose, a very tall forehead, and a very small/smooth jaw... So she just has extremely neotenized features. Even in her 30s, she still has a more youthful appearance than most 15 year olds. She really may be the most beautiful woman of all time... She's certainly the most beautiful woman I've ever seen, by far.

I'd argue that there's much more to beauty than the traits that you listed. There's room for a lot of variety, and many people find CR's exaggerated features more spooky and evocative than beautiful. A lot of it is down to personal taste, among other things.

But I'll agree insofar as her face is one of my favorites, if not my favorite, to watch on film. Her eyes could melt a glacier.

I agree, the eyes have it!
Windows to the soul and all that.....

True beauty shines from within.

*****************
Some men are dogs, some men are wolves. I am a lion.

"Extremes" aren't perfect though, that is why they are referred to as extremes. I think that Christina Ricci is very pretty, but she is far from one of the most beautiful actresses I have ever seen.

Her big forehead is the only thing that spoils her features.

She was SO FREAKIN' HOT in Black Snake Moan!!