My favorite piece of content is the Post-Moogle questline. So much lore and world-building in those quests.
Closely followed by the MSQ.

Bozja and Eureka may have some good parts, but if so I never got far enough to encounter them before I got sick and tired of the whole crap.

Several of the older dungeons/trials/raids were fun to run, but the newer ones where the only real mechanic in the boss fights is to avoid the AOEs is not much fun. I despise that particular mechanic.