The fourth installment of the The Sims is coming out in fall, which will undoubtedly bring the number of Sims games sold to a grand total of a gazillion copies. It’s already the best-selling game on PC of all-time, and we were wondering what makes a simulation about the ins-and-outs of everyday life so incredibly popular. The easy answer is that Will Wright created it; and that it has broad demographical appeal; and you can kill your Sims by having them get in the swimming pool and then removing the ladder. But that’s overlooking the possibility that The Sims is…