Now that the X-Com games are out on Steam for ($5 each, $14 for all 5) and all but Terror from the Deep run on Vista, it might be interesting to see new people try at least the first one.
Non US people may know them as the UFO series. They are a mix of RTS and TBS. The first one is great, the second is basically the first one, but harder and right now vista incompatable, but they're working on it. Appocalypse goes a bit more RTS, but is still fun, the others... The package is still a nice deal.