well the aztecs were definitely the most advanced, they made great strides in mathematics, and astronomy for people of their time. but the romans were much more powerful, they built up an empire almost twice as large as any other in history, i guess it depends on what you mean by "great"
china was pretty amazing for all that they discovered. Egyptians for what they built and discovered. But I would say the Japanese for having the most culture and heritage.
It would have been a completely different world to live on that island completely secluded for that long.