In "Kingdom of Jerusalem" when Saladdin (Ghassan Massoud) is asked how much the holy city is worth he says "Nothing and Everything" what....?

I think you mean the film 'Kingdom Of Heaven'.

He says Jerusalem is worth Nothing and Everything because it similtaniously is both.

Its worth Nothing, because ultimately its just a place. Its a pile of stones, and at the end of the day has no tactical advantage other than being wanted by everyone. Had everyone involved been atheist, nobody would have cared about it.

But its worth Everything because its a symbol. Its considered sacred by both sides, so its capture cements Salah ad-Din both as a great general, and a divinely inspired military leader.

Salah ad-Din recognises both its value as a sacred symbol, and its value as a ruined pile or rocks.

He probably means the city itself isn't really worth the trouble, but geographically, politically, and historically, the city is everything.