I find getting Fan fiction posts, short stories, long replies to posts, "original and well written" articles written by a forum member, how to tutorials, tips and tricks related posts, and "original" fan art, graphics, photography, video related posts to be the rarest types of post to get for forums.
Usually posts with large amounts of quality seem to lack. It tends to be nowadays that a large amount of people just go for short simple posts.
However, with some gaming forums that have weekly updates from members, the posts seem to be longer. An example of this would be someone updating their Football Manager save.
Indeed, it seems the length of posts and reply are becoming simpler and shorter thesedays sort of like Twitter twetts and Facebook status updates.
Although, on forum promotional related forums, a few members write detailed tutorials on getting more back links, traffic to a forum, and promotional related topics which are a few hundred words in length.
