FF4s crystals are good but its a bit wierd.

there are the four crystals.
the four dark crystals.
the crystal on the lunar whale.
those crystals in FusoYas crystal palace (or are they the same as the 8 crystals of dark and light.)
and also the one golbez gives to cecil in the final boss fight. where'd that one come from or was it one of the ones mentioned before.

overall, its pretty confusing.

the crystals in FFV seem less important when you get to world 3. but in world 1 and 2 there good.

FF1s just plain and simple.

FF9s is probably the coolest crystal and probably my favourite.