Postgame has come up a lot lately on both sides of the arguments about these games, so I'd like to get a clearer idea on what is considered a good postgame. Obviously a full battle frontier is widely accepted as the gold standard, but what about smaller battle facilities? Are new routes and dungeons that you unlock after beating the league an acceptable substitute? What about Legendary sidequests? Contests? Gym leader and elite four rematch teams?

What do you think is the minimum amount of postgame content that would make a modern Pokemon game good?