From what I remember from the good ol days and why the Xbox fans are no longer as active:
1) they started dwindling and losing confidence when the ps3 started picking up steam. Most threads were about how the ps3 is being beaten by the underdog and how Sony will go bankrupt due to xbox dominance and being in the red.
2) many found a safe haven with MisterX
3) Nintendo and Sony fans have thicker skin than Xbox fans and can handle more abuse which is why they can stick it out over hard times.
4) a lot of the best threads came from sales gaps closing, big games going up against one another, scores and sales. These things no longer seem to have as much value due Sony dominating most charts.
5) Megatons - the threads that were created when popular Sony only games or known as Sony games although mp came to MS or had bigger MS affiliation:
GTA
DMC
Tekken
Final Fantasy
Many other JRPGs
I offer the Xbox community a thread idea:
Why killer instinct is better value and offering than SFV.