Well it was certainly a thrashing by Australia, but you also have to look at the circumstances for Sri Lanka. They had to repeatedly come on and off the field, play for the most part on a damp pitch with a damp ball and with varying amounts of light. You cannot really say that both teams batted in equivalent and fair conditions.
That's not to say that Gilchrist's innings wasn't spectacular. In fact, if Gilchrist hadn't gotten going or one of the chances were taken, I suspect the result would have been different, or at least, the match would have been much closer.