My housemates and I have been playing Worms Armaggeddon incessantly for the last two weeks. Such great multiplayer!
As for computer classics:
Baldur’s Gate II and Throne of Bhaal Expansion: I would argue that it’s the best computer game ever. It has everything: a great story, intelligent and diverse dialogue and characters, and intricate gameplay (extracted almost directly from AD&D). The music is better than anything else I’ve encountered in computer games, and is more emotionally mature than most console RPGs’ music as well. The graphics are excellent, for when the game was released.
Might and Magic VI: A first-person, real-time adventure with wonderful and addictive gameplay. Modern MMORPGs could learn a great deal from it.
Heroes of Might and Magic I-IV: This series is an offshoot of Might and Magic, transformed into turn-based strategy. Heroes shines in its multiplayer mode, where its unorthodox “roaming the countryside, turn by turn” approach becomes incredibly catchy. Heroes II is the best of the first three. Heroes IV, my favorite, alters the series by making heroes playable characters in battle, a la Warcraft III.
Master of Orion II: A space strategy game that closely resembles Heroes, with a little less “roaming the countryside” and more micromanagement.