FF9 has lots of references to past FFs and even other Squaresoft games. This is the first time I've heard that it resembles FF5. I've heard that it resembles FF6, and I myself think it's more like FF4, but I didn't think it's like FF5.

Cid isn't such a big deal because every FF from 2-10 use a character called Cid. The name of (SPOILER)Necron's Grand Cross might be from FF5, but the animation looks more like from FF7 or FF8 (a spell that involves many planets). The fanfare music similar to FF9's is used in FFs 1-6. Gilgamesh has also appeared in FF8. I can't remember if he was in FF6 as well.

But if you asked for similarities, here's one: (FF5 AND FF9 SPOILERS)There's two worlds, and a villain character (Exdeath or Garland) tries to merge them into one. Although Exdeath did that to unseal the Void and Garland did that to give Gaia's souls to Terra's people. FF9 also has a summon called Atomos, which was a boss in the tower where (SPOILER)Zeza dies. In both games, the (SPOILER)final boss will try to destroy all reality, Neo Exdeath by sucking everything into the Void, Necron by turning everything into the Zero World.

I'm sure there's more, but I'm too tired to write more right now.