My fave is the first sims. I absolutly loved it even though always ended up killing my sims bc everything burned down xD I dont know if it was in the other sims games as well, but I LOVED doing stuff on that chemical table, i remember that you could get evil doppelgangers walking around if you drank it. AND THE EXPACKS OMG. Still remember playing so much with that magic expac and these black holes you could buy, oh man nostalgia is taking me over  
I loved sims 2 aswell, always had a beachhouse with too much CC ahaha xD And the cheat codes where much easier back then. There was so much to cheat and it was awesome for me xD