I preferred Sims 3, I never played Sims 2 so can not comment on it.
Sims 4 is ok but I do get bored with it.
I miss the colour wheel of Sims 3 and the open world.
I also do not like that there is no story progression for sims that move out and you no longer play, they just grow old and die.. At least in Sims 3 they would progress with their lives, meet other sims and have children.
Also in Sims 3, there would often be a new world released that you could buy, you don't get that with Sims 4.
I always have felt that Sims 3 could have gone on alot longer with more expansion packs and add ons, it was put to rest long before its time.
Sims 4 is ok and I do play it and have all the packs that go with it, just for the sake of having them, but I feel we are very limited with it being a closed world and also a lot of the time when I am making a new sim or building, it is spoilt as not all of the items match the way I feel they should i.e. the colours don't match and it messes up my idea of what I want my sim or building to look like.