Alexander the Great's conquests led to a new era known as the Hellenistic Age, because the Greek culture was spread to the conquered lands. Without Alexander the Great to conquer those lands, the Greek culture may have remained within Greece.
Alexander the Great destroyed the Persian Empire, conquered Egypt and continued east until he reached India. He did not conquer India because his troops refused to fight anymore, but the areas he did conquer were massive. The Greek influence in these regions became popular in the arts, exploration, literature, mathematics, philosophy and science. Although the indigenous culture influenced these new kingdoms as well, the majority of the changes occurred by incorporating Alexander's culture into the newly conquered kingdoms.