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I like my FreeCiv and Freecol. EDIT: And OpenTTD. Edited 2011-11-14 13:00 UTC
Yet all 3 don't fit into you categories.
True but then again, most commercial games are just rehashing the same stuff over and over again so it's not that different, really.
Not to be picky, but OpenTTD looks pretty much like the first version of SimCity I played.