It's true that standards of beauty have changed radically over the centuries. Judging from a twenty-first century perspective, I agree with you, Ilyala, that Anne Boleyn was the stand-out beauty of the bunch. At least if the Hever portrait (which shows her holding a rose) is any true likeness. Here her features are shown as small and perfectly symmetrical. She bears a strong resemblance to her daughter, Elizabeth, except that she has a shorter, prettier nose and much darker coloring. I suspect it was the dark coloring and the absence of much of a bosom - not to mention her commoner blood and her status as Henry's great love, supplanting Catherine of Aragon - that made snobs like the Spanish ambassador Chapuys describe her in largely unflattering terms.
Prince Lieven is right that Anne must have possessed the "It" factor, that indefinable element of pure charisma that Henry himself had. And she must have had it in spades, because she wasn't royal by birth, and being royal is half-way to being thought of as "charismatic."
Jane Seymour, judging from the Holbein portrait (and Holbein's portraits were judged extremely realistic even in his own day), was just plain weird-looking. She looks like a mildly barmy Miss Priss schoolmistress about to discipline the class. Or a nun about to do the same. I can't imagine what Henry saw in her. Maybe he felt better knowing that she wouldn't cheat on him (as he no doubt suspected Anne of doing) because no one in their right mind would find her even remotely attractive. Just kidding... sort of.
The Holbein portrait of Anne of Cleves is indeed ravishing but if you actually look at the features of the dreamy model princess they're not all that exceptional, in fact they would be rather plain in another, less opulent setting. But I think it was Anne of Cleves' lack of knowledge of the courtly arts that really turned Henry off. She didn't recognize him at their first meeting, when he had gone to so much trouble to disguise himself as a dashing, handsome stranger, and she didn't know anything about music or dancing either. She was a provincial, in Henry's mind a country bumpkin and an insult to his intelligence (not to mention his vanity).
Catherine Howard's portraits are singularly unflattering. All I can say is, she must have had an exceptional complexion and a really voluptuous body, not to mention her own dose of the famed Howard charisma, for Henry to have fallen for her as hard as he did.
Katherine Parr seems to me completely average in looks, but I think Henry was attracted to her for other, less superficial reasons - her intellectual interest in religion, and her reputation as a nursemaid-wife of ailing old men.
