He's serious. I'm a D&D player and you can find a LOT of things in common. I shall make a small random list.

-Some classes, like the Thief which is one of D&D's most classic classes. Also, the basic Mages (White, Black and Red) are the same of the basic Dragonlance campaign setting.

-A lot of spells, sucha as Haste, Levita(tion) and the like.

-Monsters galore. These include Sahagin, Ghoul, Wraith, Mind Flayer (one of D&D's most famous monsters!), dragons (duh), Lich (in FF 1 , it is the Fiend of Earth, and in FF IV the Fiend of Earth is an undead creature as well), and Tiamat, which in D&D is the goddess of evil dragons and is represented as a many-headed dragon.

This is just something to begin with. I'm sure Kishi or someone else will come and make a more complete list. Actually, I always wondered why those who have the rights over D&D didn't sue Squaresoft back then.