The parallels between Wonder Woman and Xena are rather interesting.
Both are battle tested princesses. Both have had dealings with Ares, all the great gods and fought with Heracles. Both have had dealings with the Amazons.
Also both became strong feminist or at least "girl power" icons.
So why did we never see them together?
Well we were. But it never happened.
According to this, were supposed to get a Wonder Woman/Xena crossover.
You can read the article there, but in truth this could have been great fun. Xena, the character and the TV show, owes much to Wonder Woman. Watching them stand together (cause you know how that has to be the end) would have been great fun.