non-gravity on 17 March 2011
Empire Earth would be an Real Time Strategy game and Civilization a Turn Based Strategy game
I recommend:
Age of Mythology - RTS
Rise of Nations - RTS/TBS
Rome Total War including Barbarian Invasion expansion - RTS/TBS
Medieval 2 Total War - RTS/TBS
SimCity 4 - City Building/Simulation
Rollercoaster Tycoon 1/2 - Simulation
I admit these are older games, but as typical PC games I value some of these most highly. I'm going to suppose you have access to console games otherwise there would be a lot more multiplatform title that I'd recommend.
I'm no expert on Civilization V, but if you're thinking about getting that you could consider getting Civilization IV instead
