First things first, I managed to limit myself to only a further two games on Steam: Medieval: Total War and Street Fighter IV. No more. Honest.
I played a bit more X-COM: UFO Defense over the past couple of days. The game is just as good as I remember it... For anyone who's not played it, it's a turn based, squad level strategy game. You spend a lot of the game looking at a view of the planet (the Geoscape), managing bases and budgets, manufacturing weapons for your troops, attacking UFOs wth your fighter jets, all that jazz.
When a detected UFO lands or you manage to force one to crash, you can intercept it with your troop transporter and the game switches to an isometric turn-based form. Here, you stomp your troops about killing aliens (or, more likely, have aliens kill your troops).
There are a bunch of nice touches in the game; for instance, you have to keep your funding countries happy or they withdraw funding from the project and, if you don't monitor the skies above their countries, they may eventually be infiltrated by alien spies and sign a pact with the invaders. In fact, advanced scanners can reveal what mission a UFO is on before you attack it; terror ships land in civilian population centres and scare the bejesus out of everyone, scout ships look for your bases so the aliens can attack you directly and supply ships resupply secret alien bases (so they can be followed to locate those bases or simply ambushed to replenish your stocks).
The other thing that works well is how you research alien technology. Just about all of the alien artefacts in the game can be researched and put to use against their inventors. While you feel completely outmatched in the early stages of the game (especially as your troops' standard armour only provides minimal project against a violent sneeze directed against you), you eventually learn to use the alien weapons and armours and even combine alien and earth technologies to make your own spacecraft.
Anyway, my favourite part of the game is its atmosphere. The music still sends shivers down my spine, and heightens the tension you feel while waiting for your turn; the game only shows you aliens that are visible to at least one of your troops, so you often spend the alien turn staring at a screen saying 'HIDDEN MOVEMENT', listening to doors slamming around the map, desparately trying to work out where the aliens are hiding. I maintain that UFO Defense and its sequel Terror from the Deep are pretty much the only scary strategy games (and turn-based strategy, at that) ever made. I would even go so far as to say they would rank quite high on my list of Scariest Games of All Time.
Right, I'll be back to write more about my new games when I get back home to my PC. Hope everyone had a happy new year!