What I'm about to say is not meant to show disdain or contempt of anyone. I only mean it matter of fact and presume there's some Archetype here that I'm not seeing, perhaps because I grew up more with scifi/fantasy than romances. I suspect it plays into that only the protagonist/reader/viewer can see the good side and thus he will be forever grateful to her for that and be completely devoted to her, though that doesn't explain to me how it seems almost inevitably they also prove to be a threat to the heroine at some point, or how it's supposed to be so romantic when Edward tells Bella he wants to kill her...at least Angel watching Buffy sleep was shown as creepy than lovely.
Obviously, I'm referring to the look of Edward, and also early Angel (that he couldn't quite keep past Angel season 2), and others, like Stefan from the Vampire Diaries. Despite how he must prove to be a threat to the heroine at some point, they also tend to have bland personalities, at least that's how I see them. Not even Angel came off as particularly interesting to me until somewhere in the middle of season 2. Like the bland look, the bland personality is also a stock in trade. (That said, in these cases the heroine is usually far more bland than the vampire love interest himself so that the audience can project themselves into her, which was thankfully avoided in
Buffy.)
I'm really trying to think of "sexy vampires" and I guess it's that I prefer vampires as demons and monsters (though they can be seductive, it's the seduction of a venus flytrap), though I was a fan of a few vampires (who I saw as tragic figures) like
Jander Sunstar (and I loved his suicide, playing an ode to the sun and sungod which he worshiped as a mortal for dawn, and when I later heard the authors, who loved the popularity of the character and so kept him around as others would Spike, I was furious for him that he was deprived his noble end just so the creators could make more bank off him). I feel as if I'm forgetting an important character which I'll share later if I can ever remember.
Still, I thought the vampires, male and female, of the Lost Boys were attractive and interesting with romantic tension I could sympathize with (cheesy effects, especially at the end, aside). Perhaps it helped that I saw it (on video) as a teen myself.