I feel the sims 4 is really empty too, but rather than content, I think the blame lies in the coding of the sims themselves. There are a lot of great items in s4, like the woodworking bench, the jungle adventure statues, and the wishing well, but unless directed, my sims never want to try these items on their own. Instead, they gravitate towards the tv, bookshelf or computer, regardless of traits, making every sim feel like a clone.
This clone-type behaviour makes s4 feel emptier to me, because there are no unique crazy characters (except maybe vlad??) that your sim can meet, so I've yet to be surprised by another sim. While s2 is just as closed off, sims and pets that walk past the house all act differently eg. some will knock, mess up your garden or rant at nothing. It makes the world feel full, because it's filled with different personalities.
