I'm pretty sure mine is all the little details, like serving meals properly and children getting onto chairs differently than adults and the way that children would run to greet their parents when they got home from work. These little things just add so much more depth to the game and really just make it different to the the others in the series. :lovestruc

Everything.

I'd have to say it's the way it's so open to different playstyles. Whether you want to play just one family, or a whole bunch of them; whether you like to keep your sims' lives idyllic, or put them through the wringer; whether you micromanage, or play as hands-off as you can; whether you play a vanilla game or fill it with mods; whether you try to complete a challenge, or play out a storyline, or just goof around... TS2 allows itself to be played in so many different ways.

I agree with the above...to me The Sims 2 is a game that only gets boring when the player is uncreative or unimaginative. If you have imagination then you can make pretty much anything you want from the game happen (see: all the medieval themed stuff and other mods for example).

I like that I can tell stories with it, including vast narratives involving whole towns, or simple individual stories. I like that the sims themselves are charming and quirky, with a real sense of personality (contrary to what The Sims 4 devs would have you believe, Sims have in fact possessed personalities and fine-tuned emotions since Sims 2..arguably Sims 1). I like the unexpected little details, things like sims in the cheap shower getting mad if the toilet gets flushed because the water goes cold, or when sims cry or get angry about events that happened days ago. I like that you can create whole neighbourhoods.

EDIT: clearly I can't answer the original question, because there are lots of things I love about the game and I can't pick just one favourite

Aside from the small details, which I also love, I like the genetics and the support for long term families.

Oh, or perhaps - some of the descriptions are really great. I like that little remnant of TS1-era humour.

Actually I think my favourite part is the customisability of the game.

Not an easy question to answer. There's so much that I love about The Sims 2. If pushed to choose one aspect, possibly the Sims themselves; there are so many characters in my game that I really care about and look forward to meeting. TS2 Sims can develop real personalities. And the creative tension between what I want my Sims to do and what they decide to do for themselves.

I thought I was immune to the charms of computer gaming before I bought my £7 copy of Double Deluxe!

My favorite aspect of the game is control of the sims. I like that the player is put into a God position. I get to control everything, and what I think is bad or evil, I can enforce, and what I really love, I can reward. Or sometimes, I can let bad things happen unpunished and good things unrewarded... in lieu of a bigger plan that I have.

That the game is no longer really controlled by EA, so we don't have to fear updates, or patches. We've got the game we want.

I love how we're over 10 years down the road with this game and it still continues to surprise me.
It makes me laugh and cry and feel like a giddy little child even at the mere thought of playing it. I have so much love for this game, I couldn't possibly choose one thing. Like OP said, all the little details. They are everything.
I love getting to know my sims and watching them thrive in the environments that I put them in, watching them connect with each other and how their lives shape out over time. Like watching them going from being alone in a crummy apartment to living in a big house with three kids, a car, pets, a treehouse in the yard... and that you can do the completely opposite of that with another sim/family, if you want.
It's a beautiful thing and such an amazing and wonderful game

For me TS2 remains the yardstick against which all other Sims games are measured. The sheer quality and timelessness of it is almost mind-blowing, even more-so after ten years and the release of newer iterations. I have no desire to play any other version at this point when the Sims are utterly charming, the game has practically unlimited depth and versatility, and it captures my imagination like nothing else ever has.

So many things I love about the Sims, I guess that why I am still playing the best of the best which in my opinion is Sims 2.
But my "most Favorite" is what I call the beat down, get Slap, push, poke, throw drink in face, get insulted.
Then The "Big Beat Down" the fight or for a better word get your Sims butt kick so now stay out of my path, you Sims fool and don't mess with me because I am not the one to be mess with.

Actually, it's the odd quirks of the game that really grabs my attention-like how a pixel will react to some commands: personally.
A lazy one will drag their butt doing cleaning, a romantic one will fist pump when allowed to pursue their romantic conquest...then there's the times when they'll turn to you and look as though to say :"you really have got to be kidding me!"
The immediacy of that look is a mindblower when you see it, once or a million times. They know what we're thinking, and they think we're crazy!

And they're right!

I love how imperfect they are :-)
Like Ripp, such a slob, I try to let him be but he lives in a dorm - so sometimes, I tell him to clean up his own puddles. The way he looks at me!!!! It cracks me up. Poor Ripp. I'll get you a maid once you have a job.
Or General Buzz. Grumpy man, overall, right? Except he has the biggest ear-splitting grin I've ever seen when holding a nooboo. I want him to keep having babies forever, just to see this smile! Nooboos are just too cute, too.
Ophelia? I thought she'd be boring. Boy was I wrong. She's hopelessly bonkers.
Tonight Circe got demoted. She came home depressed, and also very hungry... deep orange hungry... Loki served her a steaming bowl of Chili Con Carne, but she was just too sad to eat. I *couldn't get her to eat* for a while, long enough that I was starting to get worried. I felt for her.
And "my" sims - the CAS ones, and their children ? You don't know them, but I promise, they're the same. Imperfect. Surprising. Always amazing.

There are so many things!

I like that the sims have a lot of personality and a lot of life, even babies and toddlers. I even like their little idles, and that they don't just stand around doing absolutely nothing even when they're just standing around doing nothing (if that makes sense). I like all the little, quirky things that never really get old. I like that it's not that hard to make pretty-looking sims. I like that even 10 years later, I can stumble over peoples pictures of the game and suddenly realize 'why haven't I seen that in my game before?' or 'why haven't I thought of doing THAT before?'. I like that I always feel an urge to play the game, even when I've not played for a while. I like that I always feel inspired to make stuff for the game, even if I end up not playing with most of the stuff (I probably have a ton and a half of CC stuff that I've never used, but don't care because all of it was fun to make). And pretty much everything else. Sure, there are a few annoying things, but nothing a mod can't fix. I also love it that while we've got two other games to play around with, it seems that the TS2 community is still going strongest.

There are three things I miss that CC can't do anything about: Making stuff move in a controllable way with the sims or other objects (for car seats, strollers, shopping carts, you name it), a prettier neighborhood seen from lot view (the LOD is really annoying) including a more open neighborhood, and a fixed baby stage (proper skeletons and face structure from parents).

I'm gonna have to go with the Mendelian genetics. I love seeing what my sims' kids look like. Also, for whatever reason, I find the Sims 2 camera to be much more agreeable than TS3 or 4.

The graphics, the life they have, the options, it doesn't stain my computer, they're extremely customization.

Oh, and one more ting. Babies!!!

Yes, they lack skeletons and face genetics, but they're still adorable, and I've loved them ever since I started playing - even back when they had only diapers, or at best some crappy default replacement outfits.

Emotions what you didn't expect to see especially in these rare situations where your plan is going wrong...
CAS with unlimited fantasy for creating a sim. (especially with new mods for sliders )
Ability to create whole sim-world.
Game has not these typical game things (the end, you won, you loose) and you can play it forever.
Unlimited different styles to play.
Offline play and you can return where you saved.

Themed Neighborhood
I can easily create neighborhood by create a terrain from Simcity4 and just put trees, buildings or rocks on a neighborhood. Each neighborhood has a different theme. Nowadays Life, Medieval, Futuristic, Cyberpunk, Stone Age, Etc. I can do it what i want.

You buy, i sell
I love how i can buy clothes, foods or perfumes when i need it. You can't get a new cloth unless you buy it from a store, unlike TS3 that you can get new clothes from a wardrobe. You need to buy a food stock to your fridge. You want a new game ? just go to the game store and buy it. If my Sims need it, i can sell it for them. Just open a store on community lot and wait for customers. I can go to that lot anytime, and see the economic system running in my town.

Interactions
Sims in TS2 have a life. I love when my Sim often came to talk, to hurt or to flirt with my another Sim. Personality points has a lot of influences to my Sims when free-will mode turned on. Nice Sim loves to compliment everyone, Grouchy Sim loves to annoy everyone, Slob Sim can eat a food (or gain money) from trash can, Etc. I like to play with free-will mode enabled and watch my Sims do anything what they want on that lot.

Custom radio and music
Because i love the music and i always turn a radio on in game. TS2 can create custom radio station so i can put my songs into a new playlist and just turn it on. I can put my songs into a buy mode or a build mode too. Each district in my neighborhood has a different songs, i can turn it on or off when i want to change my playing district.

Cheats !
The Sims may be the only game that i should play it with cheats and it's fun. boolProp testingCheatsEnabled true can do anything. I can change personality points more than or less than 25, kill this Sim by rolling a hunger mood to the red, create a new NPC or towny in game, selectable a Sim to do something what i want, anything i can do. Too bad this cheat has a less power in TS3.

Don't worry to other Sims in town
I don't like a Story Progression in TS3 (I don't say it's bad, but it's not fit for my gameplay style) I just want to control all Sims in a lot, and it doesn't bother other Sims in town. Don't worry about move-in or move-out, fall in love, has a new baby, Etc.

One Sim, One Life, One City
He can be a mafia and a nice-guy, she can be a great woman or a bad girl. This guy was imprisoned in a jail, this guy is a dirty-hobo, she is a famous celebrity in town. I build a hospital, jail, bus station, school, landfill, anything in one lot and one town. It's a freedom !

Others
It has a lot of things to tell you more, but i forgot it. If i notice somethings why i love TS2 i will tell you more.

Quirky Maxis humour. Amazing stability and framerate. Easy customization and built-in mod support (This is a huge positive for any PC game I play) and its visuals believe it or not.

It may be 10 years old but the game still has many positives going for it, and I hope that even with the release of TS4, fan sites like this and many others will continue community support for it.

The possibility of having multiple, controllable families in the same neighborhood. That, and saves that don't corrupt randomly. I think this is the main reason why TS3 never managed to capture me.

Can you really only play one family in each neighbourhood (I think they call them "worlds") in TS3? (I've never played TS3 -- I don't think it would run on my computer -- so I honestly don't know.) How could they possibly think that was progress?

In Sims 3 you can switch to another family but if you will do this, you will loose control over your previous family and things can go totally wrong.

You can play more than one family, but in order to play rotation (as I do) in sims 3 you'll need to mod up your game. This way the families you switch out of don't do anything you don't want them to while you're away.

I can't think of anything I don't like about Sims 2.
Because even if you for example don't like to play supernaturals (because you're more after realism) you don't have to.
You easily can just let that be. Or you can mod out basically most of what you don't like.
Or add what isn't there but could be there through objects, mods etc.
So, to say what I favor most is the customization.