Hey guys, I've been reading this topic for a while and thought I'd contribute on the whole Lucario discussion.
According to IGN's Top 100 Pokemon poll (where over 14 million people voted), it says that Lucario is the 32nd most popular Pokemon of all time. While that's actually really good, it isn't quite the most popular Pokemon ever. Mewtwo, on the other hand, is the 2nd most popular Pokemon ever (behind Charizard). That really says something. Zoroark is already the 68th most popular Pokemon and he hasn't really had the chance to grow on anybody yet.
If it matters to anybody, I'm a huge fan of both Lucario and Mewtwo and I'd really love to see both return along with Zoroark.
Here's the link:
http://www.ign.com/top/pokemon