A few corrections:
-Descent IV doesn't exist.
-Hadn't heard of Undermountain, but after a bit of research that looks like a different game universe, not part of the Descent series. Using the graphics engine does not a part of the series make.
-The name of the game is Freespace 2, only the original had "Descent" in the title, and even then that was just the American release due to trademark reasons. Officially, the Freespace series and the Descent series are different, and do not have anything in common (beyond being developed and produced by the same people that is).
To answer your question, while many of us have played and enjoyed the Descent series, this forum is first and foremost about the Freespace series.
By the way,
