Well your apparent definition of a great thread is one with pages and pages of replies correct?
Well producing those can result from either pandering to a certain groups ego investments or challenging a certain group to think outside the box and better themselves which would then be considered a controversial thread.
The mindless pollyanna positivity threads found in the forum archive with 17 plus pages and five star ratings and those of today's Sosuave morality crew are the first type.
The second type are threads posted by Str8up and Rollo Tomassi and similar posters.
Though rarely someone might make a thread that hits the sweet spot that appeals to both groups.
I'd say joekerr31 and squirrelz were experts at those kind of posts.
Other lengthy threads can be the result of a teaching thats time has come in that it contained the consciousness raising information or inspiration that the masses of posters were looking for or some such and then it goes on to be posted in for a great long while.
Now you might wonder but KontrollerX how then does a garbage thread like the masturbation discussion go on forever when it should of been deleted ages ago freeing up much needed bandwidth which could of then prevented us from having been put under the retarded 10 post limit restriction?
And I would shake my head and sadly answer you with that age old saying...
"One man's trash is another man's treasure".
And I'd leave it at that.