I only kinda liked the first one (though I liked Selene). The way I immediately saw it is that they were mutants that would fit more in with the X-Men universe. Basically 1-3, I think brothers, had the same mutation that gave them a type of shapeshifting ability, but needed the genetic material of something else. So one bit by wolf became a werewolf, another by bat became the source of the vampire legend. Apparently it came with a healing factor similar to Wolverine (which suddenly makes me wonder, could Wolverine survive having his blood drained?). And just as the genetics adapted themselves, it also infected others like a retrovirus so others could be mutated by it, but being infected by both would cause death as the mutant virus would endlessly attack each other.
Again, that was my impression. I saw it as more of a medieval mutation that created a secret society (implying they still feared society's collective wrath). I didn't see the vampires as undead (they had a heartbeat and circulation, even if they could enter moments of hibernation, heck, Selene went into shock from blood loss at one point like any mortal which implies circulation) or magical, at least no more magical (and even less) than the mutants of X-Men. In a way I didn't even see it as a real vampire/werewolf story, not at a gut level, but more of a scifi story of those that inspired the legends (Star Trek and Star Wars are scifi and have more ridiculous concepts, heck, the Enterprise even got kidnapped by a god, IIRC, let alone the Q, etc) rather than dark or urban fantasy.
I did see the second movie but barely remember it. I remember getting bored early on. A bat-winged vampire chasing you while you drive in a truck and you shoot it is cool for maybe 20 seconds or so, but it felt like it just went on and on. I remember even less after that other than to feel the story became even more vague than it already was as another faction revealed itself.
