I like good bad guys. Let me clarify. I like really well-developed, believable bad guys. You know them when you see them. The villains that you can't help but hate, and you wouldn't have it any other way. The nemesis that perfectly foils the good guy, and if you want to know his motivation, you can find it. Sure, there's always room for a comic book villain, the type that's just bad because, well, he is. But I like the bad guy with a past. I want to be able to look at the bad guy's life and see that crossroads where he decided to be the bad guy.
The problem with so many bad guys is that they're very one dimensional. They're WYSIWYG (What You See Is What You Get). In and of itself, I suppose a WYSIWYG bad guy isn't the worst thing in the world, but it tends to lead to WYSIWYG heroes. And that's unacceptable. Your good guy is only as good as your bad guy is bad. If your villain is one dimensional, your hero probably isn't much better. Even if your hero is awesome, he/she won't seem to awesome pitted against a ill-conceived villain. I mean, how unfair is it to put up a great, well-thought out good guy against a bad guy who has no conviction and no real motivation? Of course the good guy will win. The bad guy doesn't stand a chance.
But give that villain a personality and a backstory, and you're in business! That scoundrel will give your protagonist a run for his money. As one of my college professors said (and this was only in relation to fiction, not real life), "There's no such thing as evil. There's only point of view." (Like I said, only in fiction.) The bad guy who is driven by true conviction is a force to be reckoned with. He's angry, he's conniving and he's passionate. Sure, he may be greedy or obnoxious, but his motivation goes so much deeper. A great villain truly believes he's the good guy. He's convinced he's fighting for what is best (and what's best usually involves him being in control).
We need more great villains, because only when we have great villains do we also have true heroes. And we definitely can use some more true heroes. But "the hero" is another topic for another day.