I have three girls and two boys. We don't treat them differently. When we buy something for one child, we make sure we do the same to the other four. As much as we can, we try not to give them the impression that we play favorites. Of course, they can be more understanding when it's their sibling's birthday and he or she is the only one who gets a gift.
In the next five years, though, we know that our kids will have different needs and wants, and my wife and I are (hopefully) prepared for that.