I have played 1, 2, 4 (Kain FTW!), 6 (Dancing Mad FTW!), 7: DoC, 11, 12 (Evil Cid FTW!!), and 13 (Fighting Fate > One-Winged Angel)

some of my faves, followed by the runner-up

Favorite Character: Sazh (XIII) Terra (VI)
Favorite Pairing: Locke/Celes (VI) Snow/Sara (XIII)
Favorite Summon: Alexander (VI,XI) Crusader (VI)
Favorite Villain: Tied between Kefka (VI) and Sephiroth (VII) Barthandelus (XIII)
Favorite Dragoon: Kain (IV, Dissidia Duodecim) Fang (XIII)
Favorite Fight: Gilgapimp (XII) Promathia (XI)
Favorite Cid: Evil Cid (XII) Cid Raines (XIII)
Favorite Character Theme: Cyan's Theme (VI) Battle on the Big Bridge a.k.a. Gilgapimp's theme (V, XII)
Favorite Airship: Ragnarok (VIII) Blackjack (VI)
Character I wished they showed more of: Jill Nabat (XIII) General Leo (VI)