Well when the Nightlife Expansion came out, which was the second, a lot of people were saying how that added so much to the game and gave the Sims much more to do.
So I don't know. It just depends on the player.
I have all of the Expansions except for "Out for Business" because I have no desire to run a business in a game and manage all that crap and spend my gaming time working.
So yeah. Being that I just got the Seasons Expansion Pack and enjoying what that brings to the game, I guess I'll say it's my favorite ahora mismo.
I haven't even sent a Sim to a University yet, therefore I haven't experienced the Univeristy Expansion Pack as of yet.
Being that my Sims just had a Baby Girl, I'm sure I'll be experiencing the University Expansion Pack soon enough.
Anata wa wakarimasu ka.....