Here's a topic I often ponder: who is the better villain for their respective superhero? The Joker or Lex Luthor?
The Joker is the perfect ying for Batman's yang. The Joker represents everything that Batman is not. The contrast between night and day shows more similarity than the contrast between personalities of the two. Over the years, the two have been through a lot, and the Joker has been at the root of some of the most heinous atrocities to occur to both the people of Gotham and Batman himself.
Lex Luthor on the other hand, is a (distorted) reflection of Superman. Humanity have seen them both as their saviours (one more so than the other...y'know, because of the super-villain thing) - however - is that the only distinction between them? One is good and one is evil? Both have the ability to change the world, but in the case of Lex, it has been his obsession to be better than Superman which has prevented him from achieving this.
So, who do you think is the 'better' villain for their hero?