I love how quickly people forget how brilliant Joker is. This man is not stupid. Yes, Luthor may be smarter, but he has nowhere near the personality that Joker does. Luthor operates nice and clean like, while the Joker is all out brash and unapologetic - and is still more feared and regarded than Luthor. While Lex is a brilliant character, and bold as hell, Joker, in my opinion, has been much bolder. Plus Jokers colorful psychopath is much more interesting than Lex's laid back style. I mean come on, Joker is just so much more creative. And, as far as the general public is concerned, the Batman movie didn't help out Lex's case any. Let's be honest, who was more appealing, Richard Donner's Luthor, or Tim Burton's Joker. And I don't really see that changing in the future. Joker is the most influential villain in DC's history. If you don't believe me, wait until the new Batman sequel comes out. JOKER is going to sell that movie. That movie is going to shatter records when people see a commercial featuring an even creepier Joker (hopefully) than B89's.
Also, though I know I'm probably in the minority, I think that Ra's is the second greatest DC villain ever. He has the wisdom of hundred's of years, is one of the greatest swordsman to ever exist. He Nearly wiped out the Justice League - with Batman's inventions no less. He (a human) went toe to toe w/ Wonder Woman and held his own. He has a much more vast operation than Lex or Bruce Wayne. He is Batman's intellectual equal. I mean sometimes, he's even in the position that you start to root for him. Though he is so evil, he is also so respectable. The same can be said about Lex or Darkseid, but I think it applies to Ra's a little bit more. He has also (wheter he wants to admit it or not) acted as a father figure at times to Bruce. There is obviously a deep respect between the two, which makes the relationship all the more interesting. Much moreso, I think, than that of say Superman and Lex/Darkseid hate/hate relationships.
Just my thoughts.