If there was one single phrase to describe Chrono Trigger...
Personally I can't pull it off. I can say many things about it, but to single out one phrase that sums up the whole of the game experience is difficult. I could say it's thoroughly enjoyable from beginning to end, with no slowdown in story progression or action thoughout. That really doesn't tell much about the game itself though, just the feeling I get playing it.
Anyways, if your friend hails KH2 above other RPGs there's a major problem already. KH2 isn't an RPG, it's an action platformer. Sure it has RPG elements like weapons levels and spells, but in basics it's jumping around, fighting in real time combat against monsters, and exploring levels akin to the most basic of platform games.
Maybe if SquareEnix weren't a bunch of idiots, and actually included some of the cast from other games besides Final Fantasy there might be some interest. (Seriously, they combine Disney with their own franchises, and don't take anything from Chrono/Mana/SaGa/etc?)