I enjoyed the finale but I do think it was a mistake to show Ares looking majestic and awesome in the flashbacks and then have him wear crude gray armor at the end. You should never tease something awesome only to close the movie with a lesser version. I was looking forward to watching goddess Diana brawling with another radiant god juxtaposed against the backdrop of a scorched WWI airfield and was a bit disappointed when Ares just fashioned his armor out of bits and pieces from the German's base. It made him feel more generic and statue like. His look kind of reminds me of those stone knights that the Harry Potter kids dueled when they were standing on that one chess board.
It was still cool overall but I do wish that his final reveal matched or exceeded the awesomeness of the earlier scenes.