1) The plot of RnR3 revolves around stopping a gigantic meteor from crashing into the Earth. Hmm.... Sounds oddly like the plot of FF7...
Generic plot
2) The hardest boss of RnR3? An Angelic-Looking Bishi with long, flowing hair. Hmm.... Sounds oddly similar to the hardest boss of FF7...
Generic boss
3) Take a look at Burai's new sword. Then take a look at Riku's Souleater Blade. Notice any similarities? At all?
Because it's certainly not because of the kind of sword it is

4) Next, take a look at Laplace; mainly the eyes and claws. Then, take a look at any Heartless from KH. Notice any similarities there?
Eh, a little, but I say he looks more like a generic dark enemy.
5) While we're on the topic of "Heartless"; what's the name of King's Right-Hand Woman? Heartless, you say? Amazing.
Someone had to have "Heart" in his/her name to complete the set you know.
6) One of Dia Iceburn's attacks is called "Diamond Dust". What has the signature attack been for the Summon "Shiva", from every FF Game ever made? You guessed it. "Diamond Dust."
Yeah, there definitely is no such thing as diamon dust in real life