Mercedes has many many more options than a Hyndai or Kia, and thus has many more things that can go "wrong". Think about it- with 100 complex electronic "options" (like moving the seats to your setting with the key fob before you get in the car) it's more likely you'll have a few things wrong than if you have almost none. Not alot of things can go wrong with manual windows... versus power windows with auto down and up, lock out saftey features, etc.. That's just an example ( yes I know that few cars now have manual windows, but it's the concept) . JD powers goes on the amount of things compalined about- not the % of compaints as compared to # of things that culd go wrong.
William