Not the best, but what else is there that actually involves a good romantic vampire story?
The original DRACULA with Bela?
Not 'romantic' in the sense I know you mean it, but hey, the 'tension' between The Count and Mina is really THE classic romance story.
I also suggest FRIGHT NIGHT has solid romance underpinnings beneath the vampire story.
ONCE BITTEN is about as goofy as you get with sexy vampires wanting 'romance.'
And lastly, completely over the top, POLISH VAMPIRE IN BURBANK is about vampire, well, not ROMANCE, but, huh, well ...