But the current champion must be Titan Quest, which just got a new Ragnarok expansion after eleven years. Paradox have been adding DLC to Crusader Kings 2 for so long now that we’re actually on year five (and closing in on six). Putting out an expansion that long after its original launch is an unusual move, but not unprecedented.
Empire Divided adds a new campaign to Total War: Rome 2, fours years after the game’s initial release.