Why do you think slavery was so much more prominent in the greco roman civilization than in india or china?

Given the general nature of equality in the Indian and Chinese cultures, one would not expect to find slavery. Slavery exists where there is a culture of wealth and distinction. Where there is general poverty, one is not likely to find slavery. Greco-Roman civilization allowed slaves to earn their freedom by paying off the debt of servitude. Perhaps the goal in Greece was to maintain freedom and equality by allowing one to work toward achieving equality.