I didn't play Sims 1 or 3 so this is all what I like about Sims 4 compared to Sims 2
Multitasking
NPC aging
Personalities based on a wide variety of traits instead of 6 sliders
Able to visit other sims at their homes
Travel between worlds without it having to be a scripted "vacation"
Travel to another lot and time still passes at home
Can attend university without being imprisoned in the campus world until graduation
All the things that matter most to me are gameplay and it's way better in 4 than 2. I know, I miss the kids playing tag too, but that doesn't compare to all the other massive improvements.
