Butz is a very deep character.

Well, I wouldn't say Bartz has no emotion but he is not as well developed as the characters in ff6 in my opinion. I haven't played very far but well, we can see the perverted side of Bartz in the ship graveyard when both Bartz and Galuf tried to undress Faris even though they knew she was a girl from that scene in the inn. I wish he had dashed into that room in the cave to steal a peek of Rena though.

FFV just required you to look a little harder to see depth in the characters. In FFVIII all the characters were VERY different Zell=energetic and enthusiastic Selphy=hyper Seifer=cocky cool Quistis=mature Squall=emotionally stunted Irvine=ladies man.
But in FFV the characters weren't so different. They would all appear at first to have no personality or depth. It didn't help that the scripting was so poor, but as proven in this thread, Bartz had plenty of times to shine as a character