Civilization 5, Starcraft 2, Minecraft (no RTS but lots of building!), annnnnd I can't really think of anything else.
forgot to mention that my computer isnt powerful at all haha. i have SC2 but the computer i built for it couple years back got fried by a storm.... long story... anyways i cant do too much in the way of newest games on PC.
kura - ill put a list of games like this that i know about, have played, or currently own. the dungeon keeper games are pretty aged but still very fun. they are PC and work perfectly fine on xp or win7. not sure about vista. but they are free to download now, i can dig up links if you are interested.