I'll admit it. I enjoy the vampire genre, when at least one of the vampires in the book is a "good" vampire and is behaving against the norm for his species. If done well, the character is usually one of the most interesting in the story because he is the outsider - either distancing himself from or rejecting completely his own group in order to co-exist with his prey. I find books that have all the vampires as just evil or malformed beings who only exist to kill rather boring. It's easier, IMO, to create a horrifically evil being with no redeeming qualities than to create one that the reader will identify/empathize with despite the fact that he would be a threat to the reader's existence in real life.
Besides, the vampire is the ultimate bad boy, and that's a strong theme in a lot of romance novels, whether it's an adult bad boy or a teenage bad boy in the YA novels.
Authors who go too far in explaining away what should differentiate a vampire from a human usually wind up creating a boring book, because there is no serious internal conflict. Those authors usually tend to have a sex scene in their books every X number of pages, and their vampire is just a guy who happens to have fangs.
That being said, though, I rarely read YA novels involving vampires. I just can't take them seriously enough because age-wise, I'm just too far removed from the teenage-angst portion of the characters. I don't mind that there is a glut of the books because as others have said, it is encouraging more kids to actually read books. My biggest gripe, though, is the number of my favorite authors who are jumping on the YA bandwagon and who haven't written any books for their adult market in a few years.
