Ghost love stories could totally make a comeback. Hey, it was the best part of Casper
(I woobie it--hey, I was a kid in the '90s!) and the entire plot of Ghost!
I'm a vampire fangirl myself (from way back). My fetish started with Louis/Lestat and graduated to Angel/Spike (mostly Angel). I've watched gobs of vampire movies and shows: good, bad, scary, lovey-dovey, corny and a mix of all of the above.
Angel is my favorite show. Ever.
I've seen Coppola's Dracula (I know I lose all credibility on not having seen Browning/Béla's yet), Nosferatu, Låt den rätte komma in (definitely one of the best things I've seen in recent years), Interview with the Vampire, Night of Dark Shadows, the god-awful Vamp, the corny but endearing BtVS movie, the god-awful Queen of the Damned, the bizarre The Breed, etc...
Moonlight was atrocious (Nosferatu is hotter--and I'm being serious--the lead was not attractive). True Blood has its high points (even it's awesome moments), but the porno stuff is obnoxious for the sake of being able to get away with it (and I'm not a prude). The Vampire Diaries is actually the most promising one I've seen in a great, long while.
The difference between vampires and werewolves/zombies/etc... is that the monster is a very human one capable of human emotions or human cruelty (which is always scarier than the animalistic cruelty displayed by most other monsters). Ghosts are the only other creature that really have the full range of the human personality.
There's also the forever young/old, wise soul aspect to vampirism that is really popular with female audiences. Not to mention the fact that vampire flashbacks are cake to history nerds. Ghost stories are rife with the same qualities (I would love to see more).
Angels and mermaids have also been done a few times (and I wouldn't mind more).