Final Fantasy 4. Haven't really planned on playing anything past 9, except for remakes and that "Brave exvius" because it takes advantage of nostalgia (Who can say no to having ExDeath in your party?), but I haven't really been a huge fan of Final Fantasy since past 9. The thing is: In my opinion, Final Fantasy trying to make a modern "serious" or "complicated" plot just falls down flat and just gets really, really bad. My favorite Final Fantasy settings are the old 'Kinda medieval fantasy but still got tech and such' with the basic plots, and also has stuff like the Black Mages, White Mages, Red Mages, you name it. Those basic plots just feels a lot more Final Fantasy to me.
5 is a close second since I really love the job system.