Well it'd have to be a Paradox Game, that one's a given the ability to craete events and storylines for... no-one in particular- I firstly though EU2, but that is a trifle repetitve after a while- much better to have the EU3 "WTF!?" factor
How about, just to be different- how about CK? All those virtual characters under your control will stave off the crushing loniness for weeks, possibly months- who needs friends; I've got a Dynasty!