With so many games sitting in my wardrobe waiting to be played I have this urge to get in there and play them all but I need to choose a short game I can enjoy and finish quickly before I go away on Thursday.. I've decided either dead space and prince of Persia.  
 Although after watching the Civilisation 5 video feature, I kinda want to play some RTS as I don't really play much games on the PC. 

"With so many games sitting in my wardrobe waiting to be played I have this urge to get in there and play them all but I need to choose a short game I can enjoy and finish quickly before I go away on Thursday.. I've decided either dead space and prince of Persia.   Although after watching the Civilisation 5 video feature, I kinda want to play some RTS as I don't really play much games on the PC.  "

well.. any really.. I don't really do online with the PC just something fun that's on the computer.

You have played Civ 4 correct?
 
If you're looking for TURN BASED strategy games like Civilization, Galactic Civilizations 2 is an option. I never really managed to completely wrap my mind around it, but a lot of people really like it. You might also try out Master of Orion or X-Com if you're willing to go old-school.
 
If you actually mean RTS when you say RTS, then Starcraft II, Dawn of War 2, and Company of Heroes are games you might consider.
 
If you're looking for some games that attempt to blend the two genres together, try out the Total War games or Sins of a Solar Empire.