I still maintain that Riolu is Mid tier at best. 1) 5% encounter rate (by no means good), 2) Absolutely REQUIRES TMs/Tutors to do anything (what if you don't have the shards to tutor, because something else in your party needed them?), 3) STAB before Level 51: Weak Palm or Iron Miss (if you have the shards to tutor it), 4) Doesn't shine until late game. I'm not moving on my opinion, so I'm just dropping this subject.
EDIT at anyone suggesting Swords Dance: Set-up moves are 100% terrible in-game, especially on something as frail as Lucario. I have Swords Dance on mine and it's actually been more hindering than it's been helpful.
"If you put the federal government in charge of the Sahara Desert, in 5 years there'd be a shortage of sand." - Milton Friedman