Guys, the fact Ghestal needed Kefka's help to reach his goals, doesn't change the fact Kefka needed Ghestal's help to reach his goal too. They were both working together.
The problem with Kefka... No, sorry. The problem with Kefka's fanbase, is that they often ignore this fact, and give all the credit to Kefka.

People say Kefka is one of the most competent FF villains, but he really isn't.
While the other main villains of the series were capable enough by themselves(having power and/or intelligence enough to work alone or to outsmart/manipulate/mind-control other people) Kefka wasn't, and that's why he needed to form a type of 'partnership' with another villain(Ghestal) to accomplish anything.
Kefka betrayed his partner later, true, but that doesn't change the fact he needed a partner to do the things he did until that point, while the other FF villains didn't need any kind of partnership to reach their goals(they had servants/slaves or 'puppets'[people being manipulated by them], but not partners on an equal level with them, both helping each other mutually).

Not to mention that everything was so much easier for him than other FF villains...(automatically destroying the world's surface and gaining godhood by merely pushing three staues, anyone?)

Say whatever you want about Kefka, but he is far from being a competent villain. He was just lucky that the circumstances were in his favor.