I love sims 3 so much I will never get tired of it. I too tried #4 and it's just not the same. The world feels dead and other sims just feel like zombies. They don't even have lives of their own, it's like they only exist if you're within their radius.
With Sims 3 (+NRAAS) they exist, they're real. You could be at home cleaning your counter.. but they're out partying somewhere, having babies, getting married, going to work.. you can click on any community lot and you'll see them there.. living, without you, you're not needed, you're just.. part of the world instead of just being THE world like in S4. Things happen because they want it to happen. They don't happen because You want it to happen. It just feels so much more immersive and real, I love booting up my town and I love my Sims and I love my neighbours.