Get To Work, City Living, and Get Together are my top 3. Seasons has a special place in my heart, but it was something I knew was on it's way, and I am so happy they did an excellent job, seasons have never been so well done before. It's so hard to choose favorites because I loved all of them but one. (I felt Get Famous was more of a GP than an EP).
Only reason why I voted GTW is because omgoodness the Detective career and I constantly find myself using GTW build/CAS items, even in families that don't have GTW careers. And can I say I just found someone who made a clothing retail shop with the makeover stations from Get Famous and now I take all of my sims' townie friends to all get makeovers... made me fall in love with GTW all over again... right down to the mannequins. I think it would be awesome for a Sim in the Stylist career to own this business...perhaps one day I will try...