FFX final dungeon sucked. Well I have only completed it once so I don´t remember it well but I remember I hated room where you had to catch crystals and you had nasty encounters. Also that place looked boring.

My favorite is IV. I just like how you moons core on your way music there is awesome and lots of treasure sidequests. V was nice, I liked how the bosses introduce themselves when you enter into Cleft of Dimension.

VI was cool too but what made actually enjoyable that it was multiparty dungeon. You could technically take all your characters. I usually leave Gogo and Umaro behind because I like it better when "story characters" travel through tower. I liked VII too, lots of difference places and treasures. It was like many dungeons in one.

I consider Pharos as part of Final Dungeon in XII. It is hard and long and its good for the story that it aint the real final dungeon. I always find it a bit silly that your characters can leave final dungeon to go have adventures outside. It is like " hey guys lets go get better equipment I´m sure Kefka and Sephiroth will just wait for us here meanwhile" .