Interesting question. I'm personally really tired of the archtype of a good vampire. He's broody and lonesome, he always makes the choice not to drink blood because he doesn't want to be a monster, and there's self-hatred mixed in there because he despises that he has to kill to live. It's an interesting story and there's a lot of room for development in there, but it gets stale after awhile. On the other hand, a main character who is a vampire cannot remain evil indefinitely. If he's not the villain, he's going to have to develop, and more than likely that means he's going to start feeling emotion and compassion. That's what the viewers relate to, and that's what fans of the character (who like him as a character and not a villain) are going to want.
I'd say for me, I like a little (or a lot) of bad. I liked Spike much more than Angel simply because I thought he was more interesting. He completely embraced his dark side for a hundred years, but he also developed and began feeling things. I thought that rendering a creature who was essentially addicted to violence completely incapable of committing it was a really interesting way to change him, rather than just the usual guilt. Take away the evil, and you see what you get. I haven't watched much of Vampire Diaries, but I think Damon's very much like Spike and Stephan's very much like Angel. Naturally, I like Damon more.
It's actually funny to me, because I've heard numerous people say that Spike's plotline and development were derivative. To me, Angel is the much more stereotypical, derivative vampire journey.
