God/Strategy Games to Check Out?

Is there any God/Strategy games I should check out for the PC or Mac? I’m not a big gamer and I play Command & Conquer: Generals occasionally and enjoy it (I know the graphics are terrible, I’m running a top-end MacBook Pro with Windows/OS X so I can run pretty much anything… and feel I’m underusing it for the games part!). What should I be checking out? Links to any demos I can download? Really anything in the genre. Thanks!