Yeah, it's all about the Mako. How many people have actually held that sword? Angeal, Zack, Cloud... anyone else in particular? Naturally whoever made the sword would be in there somewhere.

It seems to me that you have to consider the fact that when Tifa, with the right material, can lift up the heaviest of enemies and suplex them... a sword is child's play, really.

Which brings us on to the next question: Who is the strongest FF character based on what they actually show themselves doing in the game? Tifa must be right up there in that regard.