I'm going to have to go with Amano on this one. His character designs seem strange at first, but I grew on them. He is also good at drawing epic landscapes that fit the fantasy mood of the games he designs for.

My second favorite is Yoshida, I don't know why...but for some reason I think the designs just work well.

I despise Nomura, every character has so many belts and zippers that aren't necessary. The uninspired goth-ish look of his characters got old fast. He ruined Setzer in KHII, even though he originally made him. Added one wing on Sephiroth and Cloud and all those belts to create a false sense of complexity. His designs are pretty juvenile and simplistic when it comes down to it.

I've seen Amano's take on the FF7 cast, they look more interesting and eye catching than Nomura's style.