Personally my favorite would have to be Twilight Imperium III , a huge sci-fi 4X game.
Or perhaps the 1979 adaptation of Dune, a tight strategy game where each player takes on a role in the conflict, and almost everything you do helps another one of your enemies, so you must choose your actions very carefully.
And for two players I'd go with Twilight Struggle
Anyone still enjoy non-video gaming? Why, or why not?