Happy's Top Five Bad Guys:
1. Faith (though she's certainly not a guy and isn't actually bad anymore, the whole Slayer vs. Slayer thing was good and she gets bonus points for being hot)
2. The Mayor (he was refreshingly pleasant and quirky for someone so evil, it actually made him kind of likeable)
3. The Master (come on, the guys a classic)
4. Spike (I liked evil Spike and want him back, he was so much more fun and less wimpy)
5. Dru/Angel (they tie. Dru was just so insane she was kind of riveting to watch. Angel had the whole tragic love interest gone bad thing working for him)
Note the majority of them are vampires. Note the show is called Buffy the VAMPIRE Slayer. Why the heck aren't their more vampires? So they aren't as uber-powerful as a hell god or Caleb or Adam or an evil magicked Willow... so? Do we really need every bad guy to be stonger than the last? Why can't we have a foe that actually tried to out smart them instead of beating them into paste (speaking of which... Glory... hell god.... god?.... you'd think she wouldn't have been so incredibly stupid being a hell god and all). I think the Big Bad arms race of muscle power is just a little, um... needless and dumb. Look at Hitler, historically speaking the worlds worst Big Bad. The guy was a freakin' dwarf. He was just so incredibly evil, fighteningly charismatic, and possessed such a warped and insane version of intelligence that those traits were all he needed to almost take over the world. I'm pretty sure that ANY of the other world leaders could have dropped the munchkin with one punch, but he wasn't stupid enough to place himself in situation where that would happen.
A better bad guy isn't necissarily a stronger bad guy.