Superman in Western Comics is kind of seen as the poster boy of heroism and the poster boy for originality, he was the first who bounced bullets of his chest and saved the girl....or so we are lead to believe. But if you have any knowledge on comic lore you'll know Superman himself is not very original either. His Krypton is bascially a copy of the Moses in a basket story, and his strength and invulnerability is stolen from the Man of Bronze
Anime is another story, I still think we have not entered an anime aware age and general stereotype is that all anime suddenly has this "big-hair" , "everyone shooting fireballs from hands", " naive, indecisive, stupid and incredibly nice boy" or sterotypes within stereotypes like "black ghetto rapper " and other ethnic casting or having a round eyed innocent school girl get all magical, powerful and crazy.....but not all anime is like this, not all of them are isolated in their own stereotyped verse. Never have I seen the criticism more on the net then when I read people from the West ripping into Japanese animation just because they tried to animate a Western comic book hero.
Japanese animation can be orginal, Superman himself should not be seen as an icon of originality and even though Goku himself is not so original, his creator might have borrowed from a hero like Superman or stole a few pages from China's Ming Dynasty Literature, like Journey into the West or Adventures of the Monkey God.
I still think Goku is a lot more original than Superman