PC/MAC Strategy Games Like Warcraft II

Anybody know of any good meaty strategy games for Mac and PC that are in the same vein as old-school Warcraft II? I was wondering about Starcraft II but not sure I'm into space / sci-fi type games. I hear it's as good as playing chess though.

Also, what are the must own games for a desktop PC or iMac right now both online and otherwise? I used to love Warcraft II back in the day. I thought it was an awesome strategy game.

Thanks!