Why are Mario and Sonic rivals

Sega's attempt to compete with Nintendo came through the most after creating there mascot character Sonic the Hedgehog who boosted the sales of the company sky high. Nintendo's character Mario had been dominated the video game industry for years after his initial appearance and Sega's plan to compete was to release as many titles of Sonic as possible. In the end the Sega and Nintendo video game war began and Sonic and Mario became known as ultimate rivals. Although they are rivals they are friendly towards another knowing each other's strengths and weaknesses and respect each other.