Hm. It's either Cid or Yang. If I remember correctly, Cid was alright, but he was only an average attacker, and Yang was a bit stronger, but he wasn't around during a difficult part of the game, so he wasn't needed as much as most everyone else. I think I'll go with Yang, much as I like him.

I thought Tellah was useful during boss fights and such, so he was pretty good.