Should I get island living, city living or seasons?

For family players I would totally recommend Seasons, but my favourite of those three packs is definitely City Living. I love San Myshuno and the flair of the neighborhoods - the singing skill, Karaoke bars, the recipes, the careers and the townies are also pretty great. The pack has good CAS and especially BB, which really added items that looked used / filthy for the first time (wallpapers, carpets, counters, fridge and stove etc). The apartments can be very luxirous or offer serious challenges (like moving a Sim with the Squeamish trait into a 'Needs TLC' apartment). Even my Sims who don't live in San Myshuno visit regularly. The Stargazer Lounge, which I turned into Stargazers (restaurant) with Dine Out is still my favourite date location after all this time and Myshuno Meadows is a very nice wedding location. So while I have and like all of the packs, CL is most essential to the way I like to play the game. The only downsides to me are the game-generated festival outfits - which of course always include the cursed eyeball ring - and that the turbans can show up in cold weather wear for game-generated townies, which is just weird.