On the contrary, I've never liked an entire set of hero characters as much as I have in FF4. They were all unique, all had their own story and they had their role to play.

Cecil -
Well according to the other thread, people seem to think Paladin is far superior to Dark Knight. I wouldn't go as far as to say 'far' superior, but it did have the edge against him. I loved the way he's hated for murdering the villagers of Mist, until he becomes Paladin and gains the respect.

Kain -
As you say, excellent character. His constant betrayal to the party and to the evil of the game always kept you wondering what he'd end up doing next. But at the end he overcomes the mind powers and manages to aid you in defeating the final boss.

Rydia -
Cecil and Kain murder her mother, and yet somehow she manages to forgive and forget. The fact she comes back older makes her that bit more interesting. I think she's a good character.

Tellah -
Sacrifices his own life, knowing that meteo will destroy him, just to avenge his grand daughter Anna. Plus he says "You spoony bard!" so he's the best character ever. Ever.

Edward -
Desperatly tragic, he wants to do great things but he's too pathetic and weak. He'd be capable of greater things if he had the strength. Unfortunatly he does not, so it's quite a sad character. I like him though.

Yang -
Yeah, what story? He does seem to be a tad neglected in the game, but he's a bald monks. Bald monks > all.

Paron + Palom -
Again, sacrifice themsevles for the greater good. They were the comic relief up until their petrification, but they were amazing when you had them. Casting spells like Comet and Flare is pretty amazing for children. :P

Cid -
Now that I think about it, this entire game seems to be about sacrifice. I like Cid's character, it's quite close to that of Cid Highwind (plus I hear in the Japanese version he's the first to swear). Again his own life goes before his companions, so very noble.

Edge -
Poor guy has to witness his parents as mutated monsters, watch them attack him, and then watch them die. Poor guy. His (almost fatal) attraction to Rydia boosts their character development alittle, and he's a Ninja. Ninja > Bald Monk.

FuSoYa -
He's the one who ties up all the loose ends. He explains about Zemus and also sheds light on Cecil's father. His magic is amazing too, as far as battle is concerned.