If you want an RTS that isn't very graphically demending, try Warcraft III, and don't let people that knock World of Warcraft discourage you, they try and put that MMO shame onto anyone who has anything to do with Warcraft. The first two are ugly as shit, but they're also from the 90's, so they have an excuse. Warcraft III is from 2002, so it's pretty. I think the battle chest (with the expansion) still sells for twenty bucks retail, but online you can probably get it for next to nothing.