Why does Lucario get so much special treatment?

I understand GF giving the likes of Pikachu and Charizard the limelight since one is the mascot and the other ended up being popular, but why Lucario? Its debut was getting its own movie, then it was made into a special in game event, and now whenever one turns up in the anime it needs to have at least 5 episodes dedicated to it. Oh and of course it had to get a mega.

What made this thing special in the first place?