[Blackthorn]

Yeah, this. They don't have a ton of releases, but their batting average is insane. I can think of only one really notable failure (Artifact). So many of their other releases have been industry changing in many different ways.

[riffruff24]

And who could forget their 2010 masterpiece, Alien Swarm. To this day I believe they only created it as an exercise. It's also free.

https://store.steampowered.com/app/630/Alien_Swarm/

[thereddaikon]

It helps a lot that they self publish. Many cant afford to do that but Valve is flush with cash from Steam in a similar way to how Apple is propped up by the App Store. That allows them to pick and choose what they do and only release products they are confident will do well.