Actually, there exists a lot of different dishes very close to the original Napolitan pizza.
Take for instance the Sfiha, a traditionnal Arab dish. It's exactly identical to an Italian pizza, except that the meat is mutton.
Or the Syrian Manaqish... similar, but without tomatoes, and with a large portion of Zaatar (minced herbs).
Or the Armenian Lahmacun, probably my favorite. Basically, it's a pizza with just plain beef, chopped onions and tomatoes. But when it's cooked, you add fresh vegetables on the top: lettuce, peppers, pairsley, eggplant... that you sprinkle with lemon juice.
In France only, you have the famous pissaladière of Nice, made with a layer of slowly caramelised onions, then black olives, sardines and anchovies.
And in Alsace, you have the tarte flambée or Flammekueche, made with fresh cream, sliced onions and lardons (the kosher variant was made with duck instead of lardons). And sometimes, if you do not worry about the "fragrance" of your food (or if you want to have issues with your neighbours), you can add a Munster cheese to it.
"A man who only drinks water has a secret to hide from his fellow-men" -Baudelaire