It's not - if it were, we could agree on it
Assuming "the heavens" is everything in the universe that isn't the earth, sun or moon - and if you create the sun before the heavens, there's nowhere to put it -, there aren't many logical possibilities, are there? You managed to phrase the question in a way that practically precludes an answer.
Tolkien still managed to answer it, though. In the Ainulindale, the first things to be created (by the master deity) are the
gods. (Who then proceed to sing heaven, earth and all that jazz into being)
The Greeks did start with the earth - but it was the earth that created the sky.
In many origin myths, a world ocean was there from the beginning, and never really created.
I've personally used the "in the beginning, the gods" scenario in a creation story I wrote. So I guess that's my answer to "what would you create first".
I'd create a bunch of lesser gods, order them around and sit back with a bowl of popcorn to watch my world unfold.