Well, to begin with, let's acknowledge tastes in beauty can vary like taste in anything else. Speaking partly as one of the few heterosexuals in the conversation, but mostly from my own limited viewpoint:
Tomei's got a great body, but her face does nothing for me. Also, she's got a "common" feel that puts me off.
Cruz has a hotness (or has post-Volver, anyway), but I've always been mystified by people who call her beautiful. The nose alone disqualifies her, by me.
Having not seen Button, and having only vague memories of Hustle and Flow, I have no opinion on Henson -- except, I guess by inference, she couldn't have struck me as a knockout, or I'd have remembered her.
Viola Davis is plenty good-looking by real world standards, but in the Hollywood universe she wouldn't remotely be called a beauty.
I think Amy Adams is extraordinarily pretty. It's a very innocent sort of pretty, which I believe reads as white bread to many here, and, you know, feel free to reject it. But the repressed Irish Catholic part of me finds her irresistible in certain ways. (Also, based on interviews, and parts of Miss Pettigrew, I think she has a sly, childlike sexiness that may emerge over time)
To get back to the original point Magilla and dws raised: as they say, and as I wrote in another thread, Adams is viewed as a hot comer by the Hollywood community, in something of the way Goldie Hawn was in 1969. I'd thought that meant a likely Oscar in the near future, but now, having seen the film, I think it's possinle the future is here.
Oh, and to go a little deeper into that '92 race that Tomei so scandalously won: It's reductive to say she won simply because she was the lone American. She was also the only actress to appear in a mainstream film, competing against four art-house candidates. And even within the arty ladies, there was an odd split: the two actresses who'd dominated the critics' awards -- Davis and Richardson -- were in box office flops that got little overall Oscar recognition; the other two -- Brit veterans Redgrave and Plowright -- were in semi-popular efforts, but were viewed as having given less weighty performances. Had Richardson given that Damage perfomance in a hit like The Crying Game, voters might have coalesced around her and produced a different result.
And, yes, this appears to be an example of "vote-splitting" -- certain demographics having multiple choices, others limited to one. But it in no way invalidates the winner Tomei, who still did what any other winner through the years has: got the most votes.