"X-Com: Enemy Unknown" - classic game, still great fun.
Of the more modern games, probably "Call of Duty" series.
X-Com: Enemy Unknown is great, usually have a game in progress.
X-Com: Terror From the Deep is maybe even better.
X-Com: Apocalypse isn't bad, but I prefer the first two.
I used to like shoot em ups but they all seem to be americans hooting rag head sand monkeys and i find it very racist and offensive,
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Wing Commander Prophecy
Bellow the Root
Starcraft
ELITE
Sim City
Wing Commander Prophecy
Bellow the Root
Starcraft
ELITE
Sim City
hmm Well Chi, I read this list and think "Guy wants to go to space".
ELITE is such an masterpiece.
My favorites are probably KOTOR, Hearts of Iron 3, Victoria, Mount and Blade Warband, and the Mass Effect games.
Medieval total war and runescape. I don't play anything else.