There are several versions of the Sims, but one of the reasons that the Sims 2 has so many fans is that the genetics work especially well. Especially the recessive and dominant traits. It's a lot of fun, for example, to see a baby be born with red hair like his grandmother, when both his parents had black hair. Part of the fun for me is seeing how the genetics play out. The two red-haired twins above both look an awful lot like their father, but the girl has her mother's eye shape. I love those little details.