I'm very inclined to think that there are vastly superior cultures, depending on how you define superior or inferior.
But let's assume that we define superior culture as that which provides the best qaulity of life to the most people.
That means that every epoch's superior culture has changed and changed and changed again in the last 6,000 years or so.
Fate has a way of making what was once the superior culture the inferior one over time. Sometime the change comes from environmental catastophies, sometimes climatic changes occur, sometimes the cultures greatest strength is also turns out to be its long term weakness, too.
Islam, arguable was once a far superior culture to Chistendom's, say roguhtly in the 10th-13th century. Thiers was the vast unified culture of arts and science, math and astronomy back them while the west was basically not much better than warlordism fragmented into petty fiefdoms
China's was clearly the superior culture to anyone's if we apply the most material goods to the most people yardstick. But they so isolated themsevles from the world that they calcified their society into something that, when confronted by a aggressive West, basically fell apart for a century or so.
For those of you for whom these sorts of questions are of interest, let me suggest the following book for your amusment:
William McNeil's Rise of the West.
A wonderful exploration of why, in the last five centuries, the WEST has come to dominate so much of the earth.
I do not believe that the dominance of the Western culture was entirely written in our genetic code, but one of the more interesting things that helped us to win this hemisphere us was White Man's ability to stave off diseases that many other cultures (most notably the AmerIndians) could not.
Upon such seemingly minor things as one people's ability to survive measels and chickenpox, does history often take dramatic swings.
We seem to be living in one world now, and one where such cultural differences might not make such a difference as they once clearly did.
As we become increasingly homogenized technically, and as there really are no isolated cultures like there was until about the 19th century, I think that basically mankind is rapidly approaching that time where we all share essantially the same fate.