Are there any good parkour games on Steam?

Prooooooobably not. You may find some indie game, but the best you'll probably get are just platformers like Super Meat Boy and Electronic Super Joy

GTA IV + parkour mod = what you need

Assassin's Creed games :3

Kreedz Climbing, a mod for Half Life 2

DC Universe Online, with Acrobatic skills

Prince of Persia games?

Assasins Creed maybe even

Edit: Sleeping Dogs also has some parkour like elements, but not like you have to do anything yourself

Sleeping Dogs has a kind of parkour system.

Damnation.
Pretty cheap game, but 75% of all time u playin' it u have to ride from point "A" to point "B" with using parkour tricks :D

Saints Row IV isn't bad

Has no one actually mentioned Mirror's Edge? Pretty much the only 100% parkour game on Steam. The ones mentioned before only have elements of parkour. However, as someone else said Assassin's Creed series are probably the second closest you're gonna get.

Ones I was gonna mention have already been :D

Fotonica might be up your alley and is still waiting to be Greenlit !