Vampires + space opera = Borg.
Still want that?
Okay seriously, you could also say they're the Wraith or even go further afield for the Goauld or those critters on Falling Skies. Wasn't Rev Bem of Andromeda another of that general type? I might be veering into zombie territory now, but they're no slouches in the ratings either.
Any new space opera series could do worse than try to integrate popular elements like the eternally tragic and sexy vampire character. Or just drag in some kind of cop show angle. Either would increase its marketability.