Rabbi Pinhas ben Yair said: Why did G-D decree that grasses,herbs and fruit trees should sprout from the ground on the third day, and He created the luminaries on the fourth day? To make His strenght known, that He can make the earth sprout vegetation without the luminaries.
Midrash Tadshei 1, cited by Kasher in Toras HaBriah (found in the book The Challenge of Creation)
He then goes on to explain similarly how I said that the sun was the most of all revered and worshipped by many cultures. .......
" It is neither created at the Beginning, which might lead one to concider it a per-eminent being, nor at the end, which might lead one to consider it the pinnacle of creation; instead it is created in the middle of the process, on the fourth day."
( I guess the whole chapter deals with this issue, I just opened the book tonight).