[PvK]

True. Complexity is a very subjective and mutable term.

However, some other nicely complex games (of completely different genres - some might argue these are simulations rather than games, but they are also games), which are also some of my Favorites:

Point of Attack 2 (HPS Simulations)
Tigers on the Prowl series (HPS Simulations)
Combat Mission (see Battlefront.com)
Panzer Elite (Wings Simulations)
Falcon 4 (MicroProse)

Point of Attack 2 definites comes to mind when I think of the most complex game.

PvK