I wonder what libraries do last 3 games use because they have more lines than doom does...
In the case of WorldForge, I think it's because it's a 15-year-old vaporware "game" that was rewritten numerous times and offers several clients (2D, 3D, this or that toolkit) for the
same game. In the case of PlaneShift, I think it's because over half of the lines are XML. If you count only C++, the LoC count is closer to 500k.
Then there is Warzone 2100, originally a commercial game, with
no less than 799,999 lines of code (was that on purpose?), not counting comments and blanks!
The most interesting cases for me are those of well-establlished, and enjoyable games like OpenTTD, Battle for Wesnoth, naev and Freeciv. Most of those seem to hover around a relatively sane 200 to 300K lines.