7 has a soft spot as it was first real JRPG and it made me fall in love with them.
8 because it was the next in line following me finishing 7, and the graphical update amazed me at the time. Just hated the junction system as I didn't like using magic at the expense of lowering my stats.
9, absolute fav. The setting, the story, the ability system. Flawless.
X was a huge jump, graphically and also - VOICES! I'll always love playing this game - Infact I'm playing through again at the moment (On my Switch this time) (Didn't really like X-2 as much)
XII is another great game, shame the audio was so compressed. The battle system was innovative - but could get to the point where you didn't actually have to do anything once gambits were all set up.
XIII divided a fanbase, but I loved it. Linear, yes, but well polished and generally fun. Personally I loved the paradigm system - especially with the boss battles.
XV - I completed it, I enjoyed it, but felt like it lost some of the FF charm.