There was never a country Palestine ruled by Palestinian people. There were P'lishitim mentioned in the Bible but they were a disparate group of tribes. The present people calling themselves Palestinian are in fact Jordanian Arabs who migrated there in the 19th century.
Most people that call themselves Israelis migrated there in the 20th century, so how would they have precedence over those who did so in the 19th?
Until the 20th century there were no such countries as Belarus, Slovakia and Slovenia, either! They're all Slavs, so I guess they've got other countries where they can go to, right?
The ancestors of the people who migrated first came from Israel after the destruction of the state and the diaspora. That is in no way equivalent to either Slavs or palestinians.