There are so many things that I like, love or appreciate. I can't list them all, sometimes I can't remember them until they are in my face and it's like pow there it is and it makes me grin, so my most recent appreciations or things I'm thinking of at the moment.
The way you can build on any basically any lot while on your played sim (with cheats pretty much anywhere). Want to set up a icecream party in the park? There it is! You can do it without going back and forth out of your current played household. I do things like this frequently. If my sim needs to sleep or go to the bathroom and I don't want to send them home, never fear everything you need is here.
Not needing mods or cc to enjoy my game. This is me it doesn't pertain to others. I actively don't want in my game what the biggest mod provides. I just don't need mods in general to tweak needs or cc to add in clothing/furniture because I can always find something that works for me. I do sometimes use mods so next..
The extreme ease of mod placement and use when I want to see what's out there to enhance gameplay (usually I go for stuff that would never be in the sims).
I love how focused nearly every theme that is released or is in the game actually is. I have so many examples but most recently photography is really drawing me in. I'm just going out and taking landscape shots, sim pictures ect and it's a lot of fun. I like how involved the animations are surrounding it. Especially using the tripod. Just going jogging even, jogging with your pet... the way they notice others and even objects when they pass it's all lovely and immersive to me due to the animation focus. Yoga was another big one for me... many, many fluid realistic poses and animations, the ability to have classes ect. Dining out... I could go on and on.
The music and sounds in the game. I always have them on. Sounds of whatever seems to fit in the world you are in (I won't give examples because I'd be going on for a bit) or even the sounds the sims make when walking over different surfaces.
The gallery although I have a love/hate relationship with it because I want more tags to narrow my search. I love browsing there when I'm building a themed save I can usually find what I need or something that comes close. I love how easy it is to drop the house and how safe I feel because I'm not searching unknown sites to get this stuff.
The settings. There are so many options to me now especially since I have all the packs. I can have that weird dusty creepy area in Strangerville. I can have the lovely warmth of Sulani. I can have the impressive views in Del Sol Valley. It helps me tell the stories of my sims.