I think most people hate FF X-2 because of the style of gameplay, with mission times and whatnot, and the flawed battle system. But if you can get over these, it's still a Final Fantasy game.
Also, Cid's been in every FF game since two, and has almost always had to do with airships.
2: Cid: He owns an airship.
3: Cid Haze: He owns an airship.
4: Cid Pollendina: Again, he owns an airship. (The first time Cid was a playable character, by
the way)
5: Cid Previa: He's an inventor.
6: Cid del Norte Marguez: Non-playable empire researcher. Is Celes' grandfather.
7: Cid Highwind: Owns an airship AGAIN (The tiny bronco was an airship, but got damaged by ShinRa), and pilots the ship you steal from ShinRa later in the game.
8: Headmaster Cid Kramer: Owns Balamb, which turns into an airship.
9: Cid Fabool: Ruler of Lindblum, is playable for a while on Disc 3 when you need to rescue everyone else.
10: Cid: Owns the airship you fly in later in the game. Is Yuna's uncle and Rikku and Brother's father.
10-2: Cid: Same Cid from above, he sells clues in Zanarkand at the start of the game.
11: Cid: Airship creator in Vana'diel.
12: Doctor Cidolfus Demen Bunansa: For the first time in a Final Fantasy game, he was the villian. You fought him twice in the game, the last of which was with the esper Famfrit. NOTE: Famfrit's weak to fire and can be oiled, making him really easy. There's also Al-Cid Margrace, one of Larsa's friends.
Tactics: Cidolfus Orlandu: A playable character. There is also a sidequest where Ramza's party needs to raise a sunken ship, that's called the Highwind.
Tactics Advance: Cid Randell: Leader of the judges, is also a playable character.
Tactics Advance A2: Grimoire of the Rift: Playable character called Cid, is from a race called the Rebe, the first non-human Cid, unless you count FFIX's Oglop and Frog Cid.
Also, almost every Sarah/Sara in FF has been a princess. In FF1, she's the princess you have to rescue at the start of the game. In FF3, she's also the princess you have to rescue at the start of the game. In FF9, Sarah is Garnet's real name. Probably because Sarah in Hebrew refers to a woman of high rank.
I may be looking too much in to this.