From TS3, I miss the "no bad photos" mod. It basically just got rid of awful pictures sims with low photography level took, meaning no fingers on the lense etc. It was so practical because I loved my sims to take photos when they were on vacation, and I always knew their photos would turn out just fine with this mod installed. I wish we had this mod for TS4, I always take the same photo 5 times just to be sure there's no finger or gnome on the photo. The worst thing is that every single photo is saved in the screenshots folder so I get the same screenshot like 5 times in a row.
Another honorable mention from TS3 is a lighting mod which made the days brighter and the nights darker. I think you could also choose whether you only install brighter days or only darker nights or both. It always bothered me about vanilla TS3 that the nights were so "blue", if you know what I mean. With this mod, everything was pitch-black outside during the night, like it is in real life. The brighter days were also beautiful, it made worlds like Twinbrook and Bridgeport look really friendly and sunny. I think the mod also effected the water color, making it brighter as well. This mod made the whole game environment look so much better.
I never played TS1 and TS2, so I can't really say anything about them.
