I don't think Sims 3 had much of a genetics system (though I could be wrong). The faces never seemed to blend very well, they always looked exactly like one parent or the other, and hair and eye colour was again one parent or the other with a ridiculously high random chance of 10% or something like that. In Sims 4 I think the facial features blend a lot better, but the hair and eye colour seems to be one parent or the other again. I'm glad the random chance either isn't there, or is very low though, in Sims 3 it never made much sense.
As for future games... I'd love a genetics system like we had in Sims 2, but I guess if the only way they can do that is to have all those in depth character files which while they were great, they also made it incredibly easy to corrupt your game and after a while it just got bogged down with all the character data of deceased sims. But a system like that would be great if they could do it well. :tongue: