The PSX RPG that really need a remake is Chrono Cross. Because it was admitted by Squaresoft to be rushed and incomplete. Based on them focusing on two other games at the same time, Final Fantasy VIII and Xenogears.
While Chrono Cross was still one of the best RPGs on the PSX, it turned out to be only 3/4 complete and not as good as it could have been. A remake could make it one of the best RPGs ever.