I only had the pigs, GrowUp and Sims Transmogrifier for Sims 1 and no mods at all for Sims 3.
The ones I'd bring over from Sims 2 to Sims 4 if I could:
1. Sims 2: Less jealousy
It keeps jelousy intact for everyone except under a very specific circumstance: If a sim witnesses two other sims doing romantic interactions and that sims is in love with both the other sims, no jealousy will occur. I've yet to find a mod for Sims 4 that replicates this exactly.
2. Beach door
Any sim passing through the door changes intos swimwear (and back into everyday when they pass into the other direction).
This added so much immersion to public pool lots compared the "everyone arrives in a swimsuit" that we have now.
3. Buyable whatevers
I have buyable puddles, water, roaches and fire in several versions (fully working deadly fire and several ornamental fires).
The buyable water is a surface with a one-tile footprint that you can place on the ground or on a foundation. It allows for the creation of shallow ponds or swimming pools. Sims cannot swim through it, it is basically just a rug.
