It feels so real with so much freedom.

Game: CS Galaxies

Seriously I have never played a game or come across a game that gives players as much freedom of choice as CS Galaxies. War, peace, commerce, raise and fall of galactic power, mining expeditions, Ore refinement, Banking, crime, factions and negotiation, Pirate raids, Invasions, Betrayal, etc It is all there and controlled by the players, not some AI intelligence. It is the most REAL experience you could ever imagine.