I have been playing for 22 years. I bought the Original SIMS 1 and started to play after I put my son to bed (he's going to be 30 in May!) and next thing I knew it was 2 in the morning!
I've been playing SIMS 3 the most. I have so much fun and find I still haven't done EVERYTHING that can be done in game.
For SIMS 1 my favorites were definitely Unleashed, Vacation and Makin Magic. I loved all the EPS, but those were definitely favorites.
For SIMS 2: SEASONS, Pets, Bon Voyage and Open for Business were definitely my favorites. I loved building my flower/bakery shops.
SIMS 3. Well, I still play this game. I love all the EP and stuff packs. Seasons is a forever favorite as well as pets. I really like Ambitions, for the stuff that came with it and the additional jobs. I love Generations as well for all of the gameplay additions. I also really like World Adventures, because it allows you to use the 3 worlds it came with, but you can use the items to make your own campsites.
In full disclosure, I do not have all the packs. I do not have Into the Future or a few stuff packs. I like what I own and I have never felt like I'm missing out.
I liked SIMS Online for the social aspect. I had fun at the silly jobs (I was really good at Pizza!). But it had it's limitations.
Happy 22 years SIMS. Thanks for giving us a game to play all these years for us old folks (50+ here) and the young'uns. It's a great game to explore your creativity and connect with other folks who feel the same.