Gonzalo at Ludology.org / Videogame Theory asks where The Sims' clones are.
The most important difference between a first person shooter and something like "the Sims" is in the attention to detail and the resources going into developing it. A fps is just the good old target practice in an other scenery. The Sims are a simulation of a society, where first you have to plan the society, then you have to plan the reactions. then you have to keep developing the game in depth, and then you have to be sufficiently original that you won't be accused to stealing from The Sims. More effort in the development means more danger of something going wrong. In today's economic climate, game-developers don't take that kind of risks.