It depends on what you're looking for. I own all but two stuff packs and they all add something. I can rank the ones I do have for you.
I forgot fitness stuff, but that has decent CAS, really cute hairs, and good build objects. Don't use the Rockwall too often.
1. Kids Room (a lot of nice decor and stuff, love the bedroom set and the outfits are also really cute.)
2. Bowling Night (I've only gone bowling maybe once or twice but I adore the furniture and CAS items.)
3. Toddler Stuff (Considering all my toddlers wear a ton of clothes from this pack, it better rank high. Cute build objects and CAS items though. Playdates are a fantastic moneymaker if you're interested.)
4. Movie Hangout (Love the CAS items a lot. They are used very frequently on my YA and teen sims. The hair's are very cute, and the actual movies are nice. Popcorn = perfect for toddlers. In my game, it never spoils for some reason and they can help themselves)
5. Laundry Day (I like the CAS and the build objects are great. I put laundry in most of my homes, and haven't had any issues).
6. Vintage Glamour (Love the CAS and hair, build mode is so nice and shiny, haven't used Butler too much).
7. Romantic Garden (Love the CAS. I don't think it had too much for build buy though).
8. My First Pet (Despite the controversy, this is a really good pack IMO. It may be a little empty, but I love the small pets.)
9. Cool kitchen (It's nice and I actually use it really regularly in CAS, and my Dine Out Restaurants always have ice cream.)
10. Perfect Patio (meh, but you seem to like it).
11. Spooky Stuff (just very meh, but the floors are nice, and there are some cute leggings).
I don't own Backyard or Luxury Party, so I can't comment on those. If you have questions just let me know and I'll try to answer if I can. MFP is on sale right know, as are some of the GP's and EP's .