Yes, many people don't regard Sim Earth among it's many Sim Peers, but I've often found myself charmed by it's presentation and means. (Often the SNES version), it manages to bring a unique spin on the god game after a sort. Lacking traditional objectives or direct influence over the beings and fauna of of the planet (the Flora is slightly different and more easily influenced with terrain shaping), I tend to see Sim Earth as more a very large zen garden. See what happens. Observe. Let your mind free.
Or perhaps you can drop a bomb on your nanotech city to unleash the robots.