Before we continue, I'm just going to point out that I don't actually believe that Smash shouldn't be considered a fighter.
That being said, I don't think that Sumo Wrestling is a valid argument to support your claim. Name me another fighting game that doesn't have the goal of reducing your opponent's life to 0. And I could be wrong, but I don't think Marvel or Blazblue are based off of real fighting sports.
What I meant by different inputs can be ignored, because I forgot about 3D fighters such as Tekken and Soul Calibur.