Google Stadia has a great controller but a terrible service. Ouya was just terrible all of the way. Want to play games that'll question your sanity? Just buy the Ouya. Pretty good emulation machine though from what others have said.
Price-wise It's the best you can have for emulation, otherwise a homebrewed PS3 or Wii or WiiU are the better choices overall. But at that point why bother when you can just have an Amazon Fire Stick and flash Android on it?