There's a criticism I often hear tossed around certain RPGS that goes something like this:
Why have a super powerful boss if you get nothing for it?
For example, in FFVIII, defeating Omega Weapon grants you a little bragging rights certificate, and nothing else. Other superbosses such as Solid Arm from Illusion of Gaia offer nothing at all for defeating them. People say that this ruins the experience, putting the player through a difficult challenge but giving them nothing to make their journey worthwhile.
Then, however, there is another complaint I frequently hear:
Why did I get this ultimate weapon/ability from this superboss now that there's nothing in the game left to use it on?
With the greatest challenge of the game behind you, an ability or weapon gained from defeating that challenge loses its luster. There's nothing left to fight with it. In the Golden Sun games you unlock Iris, the most powerful summon, but even the final boss is a cakewalk compared to what you had to beat to get to it.
So, what do you prefer? Do you like being able to acquire the ultimate weapons and abilities to use against the hardest boss in the game, leaving you with no gameplay reward for defeating it? Or do you prefer getting an ultimate weapon from that boss, a sign of your victory, even though there's nothing left for you to use it on, since you can already defeat most foes just by sneezing on them?