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I have a love affair with Civilization IV--it does have some beefy requirements, though. I'd recommend a souped up MacBook or (ideally) a MacBook Pro at least.
 
I have to reccomend Company of Heroes. Fantastic Game. One of the best game i've ever played. It's a bit slow for an RTS, but I see that as a good thing. Gives you more time to think, and mind you there is alot of thinking. Have to use cover in this game.

Otherwise, Civ IV is very addictive and Oblivion if your system can handle it. If not Jade Empire and KOTOR. I wish the prequel movies with the exception of Revenge of the Sith were as good as KOTOR.
 
I am going to be upgrading soon so Civ IV it will probably be then

One thing to note with Civ IV is that, if mods are at all your interest, the Civ IV PC mod community is apparently much more vibrant (owing to more people, longer time out, etc.), so I'd get the PC version rather than the Mac native if you're interested in the mod community. Just what I heard from a fellow Mac gamer.
 
One thing to note with Civ IV is that, if mods are at all your interest, the Civ IV PC mod community is apparently much more vibrant (owing to more people, longer time out, etc.), so I'd get the PC version rather than the Mac native if you're interested in the mod community. Just what I heard from a fellow Mac gamer.

Can't mods for a game work on any platform/OS? Often they can. Much as I dislike Aspyr these days, saying "get the PC version to run on your Mac" will only hasten the final death of Mac gaming due to Boot Camp.
 
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