Which pack has been most influential in your game?

Seasons. The only thing I dislike about seasons is how my sim has to wear summer or winter weather instead of their everyday outfit. Not that big of a deal though. Seasons add depth on a small and large scale.

From a building point of view it would be Get Together. Windenburg has plenty of lots and variety. Clubs can be very lucrative when exploited and they have other uses such as preventing stupid sims leaving group events.

City Living I like a lot but I don't really want my sims living in San Myshuno and I only have sims visit festivals occasionally. The annoying neighbors remind me too much of when I lived in a town. Good for immersion but somewhat annoying for gameplay. The fact the aesthetic could be anywhere works for me, elements of NY, SF, Hong Kong and Tokyo, the sound design is also spot on.

Spa Day I use a lot. I like the wellness skill and the New Age music is relaxing, plus the build items are good for modern bathrooms. I just wish the fingernails worked on trans sims.

As for Seaons I feel its needed for immersion purposes and for the sense of time passing, but I also think weather should be base game at this point. So technically its by necessity rather than being particularly influential. I don't like the majority of the holidays, the BB is reasonable, the CAS is better. But I also can't forgive this expansion for killing off 5 sims including my sims girlfriend when they decided to go home in a blizzard while wearing their gym clothes. Environmental effects stays off from now on.

I absolutely have to have my vampires and spellcasters so Vampires and Realm of Magic.

i mean it will always be seasons and vampires cause i probably wouldn't play the game anymore if those packs did not exist itd just be too dang bright and cheery

but also theres just lots of packs i use at side and barely notice as separate packs from base game anymore cause i use them all the time but i never really dive into them completely

like without spa day all my sims would probably be overweight thanks spa day

also get to work and strangerville are must if trying to play sims 2 storylines although gtw is throughly broken and very much needs refresh

Mine is City living as well. Festivals can be very useful.

Mansion & Garden Stuff - It has done wonders for my Victorian builds, especially 2nd Empire. Think of it, Mansard roofs with properly functioning windows!

If you mean TS4, then a blend of Jungle Adventures and City Living. The former because my sims can become expert archaeologists with a handsome income source. CL because 2 of the festivals provide lots of harvestables, including dragon fruit and bird of paradise. In my game installation without seasons my sims make a very nice living being farmers.

Parenthood for varied relationships between family members that actually feel like they have some impact on my sims and Get Together for the club feature (don't know what I'd do without it really!)

Realm of magic : spellcasters are an important part of my gameplay and I have one in most of my played households. When this pack released it felt as if my game was complete, as if an essential part was finally added. I love being able to have sims with a magical nature and adore the furniture of the pack.

Other packs that have changed my game are
seasons because weather changes everything and holidays because they give a sense
get together because of the clubs which I regularly use to have groups of sims meet up
jungle adventure I never expected to be excited for this theme but I loved it from the get go and enjoy sending my sims to selvadora
Werewolves this pack is still a bit to fresh to be certain but I think it might become one of my most important packs as well. I like the werewolf occult lifestate though I don't think they will all live in moonwood mill

Seasons, City Living, Cats and Dogs, Get Together, Snowy Escape, Dine Out, Outdoor Retreat (although I think it desperately needs a refresh like Spa Day got)

City Living :)