I now know everything that I should know about you.
Your logic is typical IX fan logic. My conclusion is backed by FACTS like sales and SE's opinions (considering it's omission from KH1 and the Dissidia complaints). IX fans ignore all this and still say it's the best with nothing to back them.
I know for a fact VII and X have larger fanbases. Regarding the other two i simply stated that higher sales could signify a larger fanbase.