Iran is a state sponsor of terrorism. Israel is a democracy. Saudi Arabia is neither, but it does have oil.
In fact if you pulled your head out of your butt you would figure out that one reason why the Saudis get 60 billion in arms is exactly so that they can one day fight Iran. That and it's payola for helping infiltrate Al Qaeda.
Actually if the Palestinian situation were resolved, Israel, Egypt, and Saudi Arabia are natural allies in the region. In fact they do co-operate extensively, by proxy through the Americans. You'll note those three nations now operate with largely compatible, inter-operable military equipment.... some alliances are kept rather quiet.
The Palestinian terrorists are largely supported by Iran and Syria, which are natural enemies of Egypt, Saudi Arabia, and... Israel. Egypt has helped Israel enforce the blockade of Gaza. Saudi Arabia has spearheaded the Arab League's outreaches to Israel, such as they've been. Lebanon is caught in the middle, with Hezbollah siding with the Syrian/Iranian bloc, and other elements siding with the Israeli/Saudi bloc.