I have all expansion packs at the moment, though when I play my games the very first few to go via Game Selector are Seasons, Into the Future, and Showtime. Seasons I thought was cute at first, then it just got tedious. I couldn't have outdoorsy Sims any longer because they would always get roasted and catch fire. I also hated that 3/4 seasons resulted in a dormant garden, that seems very unrealistic for me, as I'm used to planting in the Spring to the Summer and harvesting in the Fall. I know harvesting works differently with the Sims 3 gardening, but it's still frustrating. Especially if you go for the default lengths in season. Holidays only get in the way most of the time.
Into the Future was fun for the first few times I went there, now it's just another thing I push to the side and ignore anyways, so I usually take it out. Showtime... well that was just my mistake in buying. Honestly, whenever I try to play the Showtime careers they all end up broken at some level and I just give up. The lots are placed awkwardly in every town, and if the clothes and hair weren't so cute I would just uninstall it permanently.
My favorite expansions tend to be the ones that could have been games on their own: Supernatural, World Adventures and Ambitions. Those three were money well spent. Others I have love/hate relationships with. Generations is nice and I like that kids have more things to do now, but I loath the punishment system. Pets are cute, but they messed up my story progression (EA story progression, that is). I could go on, but I think I've made my point and my post is likely dragging on.