In all honesty though, Blade himself is an abomination to the tradition as he is one of those creations spawned from the depths of the deepest and most twisted fanfiction... A 'half-vampire'.
Bleugh... It's almost enough to put me off vampires entirely. But then I remember Kain, and he helps guide me back into the fold.
Personally, I don't mind having a bit of eroticism in regards to vampires. What better way to convince a human to get into close contact with you than to promise a fulfillment of one of their most basic needs?
The split-off point is where they actually *do* get a bit naughty, and no massive exsanguination occurs.
Sex is a primal and defining characteristic of the living. The dead should have no interest in it whatsoever, other than as a means of getting what they really want. My personal take on vampires is that they are cold and emotionless killers, as their death and subsequent transformation have utterly numbed any feelings their living minds might once have felt. Only the strongest concentrations of the most powerful emotions (hate, fear, and in certain circumstances love) should have any effect on them. Beyond that, they feel only a dull, empty craving that they attempt to satiate with fresh blood. They no longer possess life of their own, so they seek to take it from others in the most basic and symbolic form.
Werewolves, on the other hand, are embodiments of the primal and savage ways of nature. By all means they should be readily consumed and controlled by whatever urges they happen to feel, as they contrast vampires by being a concentration of the chaotic and unfettered nature of wildlife. While a vampire sheds the lower instincts and needs of its former human self, a werewolf sheds the higher culture and advanced though. They're not so much whole transformations as they are simply concentrations of aspects from the original human source given shape.
This system makes it possible to add in the sly hint that it's all perhaps a series of metaphors, rather than any fantastical reality.
But then again, I suppose you could say that the Twilight series is attempting to use metaphorical depiction to address very serious real-world issues... Namely pedophilia, abusive relationships, and the blood diamond trade (come on, think about it... "This is the skin of a killer!"? Sparkly? It's been staring us in the face all this time!)
To be perfectly honest, trying to assign deep hidden meaning to Twilight is a bit silly. But it's also remarkably fun.