LOL.
Well honestly, unicorns are cool when you are under 12. Then real horses win, if horse-love is staying type. Even my horse-loving sister is more interesting about mount's stats.
And unicorn have mythology package with virgins and fey.
I despise Vampires of any type, but that's personal preferance. Vampires are teen-thing. And more commonly, sexy romance teen thing. So it depends what kinda vampires we are speaking. White Wolf already did game about Vampires, and that was popular. Mostly because it brought all the adventurous elements there, vampire politics and nasty monster qualities, and rock star erotiscm, or punk or whatever.
Vampires in western mythology have since Dracula been cursed creatures with obsessive issues with love.
There is nothing really attractive about flying head hunting for blood of chilren or savage disease ridden plague vampires.
If you want to re-sell old myth to any audiance of today you have to re-skin it. LIke movies do, or like Anna Rice did or even like Bram Stoker did or Twilight books did.
So yes, vampires would sell again. Though I think young teen rebels aka Hunger Games, or young witches (both sexes) like in Secret Circle.
But make something original rather than getting expensive rights for those mentioned.
And there is important thing to remember. Those games must attract young people of today, rather than look cool to us oldies. My tastes are very diffrent from when I was teen. And when you have heard someone get at this hobby at middleage.
If we want this hobby to survive we need new audiance, larger audiance and yes, different game. Times They are a Changing....