To speak less in analogies and just cite history, Palestine was ruled by the Ottoman Empire from the 16th century until 1917. After their defeat in WWI, Britain took control of the region under the British Mandate for Palestine, basically controlling all of the region west of the River Jordan. Up until 1947, approximately 420,000 Jews immigrated to the region where the population was about 600k Jews to 1.2M Arabs in Palestine.
In 1948, Britain left which meant an opportunity for a coalition of Arab states to attempt to take back “what was theirs” 31 years ago. The Jews were able to defend the region and have since been encroaching further and further outside of that area they defended previously.
Before all of this “modern” history, from the 7th century to the 16th, the region was controlled by Islamic states and Christian crusaders (who took the land for themselves, not for the Jews, and even killed a lot of Jews — think hundreds of thousands, if not more — during their occupation).
We can continue to go back in history to Roman rule, Egyptian rule, etc. but how far back in time are we willing to go to, going back to your analogy, determine how much of the pizza you should be entitled to? What of the rest of the world? It’s a good question and I obviously don’t have the answer but I’m also trying to understand as best as I’m able to.
With that being said, none of that history warrants the atrocities being committed by either side. If the two sides could co-exist in a United Israel-Palestine state, that would be the ideal resolution in my mind. Unfortunately, due to the overwhelming religious zeal on one side and a superiority complex on the other, that’s just a pipe dream.