Another great "open world" type game is S.T.A.L.K.E.R. (three games in all: Shadow Of Chernobyl, Clear Sky and Call Of Pripyat).
And one final suggestion:

"Boiling Point"
I featured this screenshot in my quiz in General Topics ("Where Am I?"... no-one guessed it) and the game, a FPS, allows for earning money doing different things (including driving buses and taxis) so as to buy weapons and equipment. How you treat other characters and parties in the "story" affects how they react to you later, so a bit like STALKER.