OK so i have some ideas for a book i want to write (all fiction) but i need help on which is best!?

I like # 1 and #2 - leaning towards a combination of the two, for example you could write a story about extra-terrestrials coming to Earth during the Aztec reign and explain it through both perspectives. That way Humans will look like an inferior species to the Aliens, but the Humans will be awed by the space-visitors...