In reply to mypyrex:
I think I'd put adjustable hinges on the top and bottom of both gates, and fiddle about with them both so it looks right by eye. If there's a half an inch difference between the top and bottom on something as long as fence posts, you could probably have both gates out of true just a little bit and not notice it particularly, compared to one gate straight and one out of true?
When fitting gates as entrances to fields and paths and things outdoors, things have never seemed to look right when everything was square, due to the ground being uneven too I think, it's always somehow looked nicer to the eye when everything was 'equally off'.
Post edited at 18:44