Due to this announcement I played some more Sims 2 and 3.
I dunno, I just prefer 2. I can see why others prefer 3 (seamless world, better graphics), but I feel that Sims 2 is the better simulation. I guess this identifies the core problem: we all play The Sims for different reasons. I like playing for storytelling and interactivity via simulation, which I think Sims 2 does better than 2.
Let's start out with just first picking a town:

We're already rewarded with a backstory, history, and a quick detail of the story for each town. I picked Strangetown due to the storylines involved. I personally love the supernatural cartoony hijinks, getting mixed with aliens, and weird scientists, and nervous test patients. It's the absurd Sims insanity that I crave.
So right off the bat, Sims 2 is an improvement over Sims 3's droll settings and neighborhood storylines. Though to be fair, Seasons and Supernatural add a bit flare to it but this is a BASE GAME TOWN for Sims 2.
My current house, made up of three siblings:
America Alejandra Cruz
America is my favorite one. She's gunning for an athletic career goal, but on the job, she had to push a piano and ended up injuring herself, costing herself a Body point stat. Remember that? When jobs in The Sims were more than just going to work and clicking "work hard" or "make friends" and they carried risks? Sims 3 aka Sims EZ mode.
Nathan Alejandra Cruz
This guy is a complete fuck up. He romances multiple women, he aspires to be a big time musician but was fired on his first day at work because some customer wanted a crappy album, and I decided to recommend they get something else in case they spare the torment. The boss wasn't okay with this, so now he spends his days sleeping - mostly because he refuses to sleep at night due to his lazy lifestyle which leaves him capable of not sleeping for long periods - and trying to woohoo as many women as possible.
Naomi Alejandra Cruz
Naomi is a party lover. Her goal in life is to have 50 first dates. You go girl.
But one of the best ways that differentiates 2 from 3 is how you customize the Sims personality. I prefer 2's approach. I like the personalities in 3, but I find that by making them perks you wittle down the personality of each individual Sim. For example, in Sims 3, you have neat freak Sims and slob Sims. Those are personality traits.
But in 2, you have a customization point represented with points.

By doing this, your Sims have a more varying degree of personality and I can't always predict how they're going to behave or react. This makes each individual interaction with other Sims completely hit and miss, just the way it should be.
More than that, beyond wants (which Sims 3 kept), Sims 3 also has hates, which keeps things more personal and interesting.
America for instance is scared of all the people she cares about in life dying. The thing is, often, fears will come up that have a high likelihood of happening.
Things I feel Sims 3 does better than 2- Seamless world
- I love the idea of personality traits such as Pyromaniac or Insane or Kleptomaniac. Hopefully they return in 4 with the addition of 2's point system.
- Better interface and controls. I can move pizzas to counter tops and spoiled food into the trash with a simple click and drag. Not the case in 2.
- The ability to change colors or patterns of ANY item. This is honestly the biggest feature I miss from 3 while playing 2.
Things I feel Sims 2 does better than 2- More Sim interaction. I'm interacting with new Sims and making friends every day. With less than a week I've held three parties, met dozens of Sims, made plenty of friends. I call them every day and they call me every day. It's easy to stay in their lives and for us to have a believable world. To me, all of what I've described is the crux of what makes The Sims work. In Sims 3, no one calls, locations are barren with maybe one Sim on the lot if you're lucky, calls are infrequent and if they are made only tailored for close friends (in Sims 2 Nathan got a call from a guy he doesn't even know just because he had an awesome date with Bella Goth), my Sims barely have any friends in Sims 3 and the ones they do are always lost down memory lane. They don't care, and I don't care. It's such a lifeless and boring world.
- Sims 3 is too easy. You don't have to do much to get promoted. In Sims 2, I'm working America out EVERY DAY so she can increase her body skill in order to get promoted. The fact that actual ramifications can come about while at work helps. I've had random fires from stoves, robberies, all kinds of shit in just the past day of play. This stuff NEVER happens in Sims 3 for me, it's all so routine.
- The aforementioned stuff.
I dunno. I guess other people prefer 3, but I'm hoping 4 is a return to 2. Sims 3 has that initial sheen that makes you think it's better than 2 when you first start, but after dumping hundreds into both over the years, I really don't think 3 is nearly on the same level as 2, one of the best simulation games of all time.