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Umm, there is a problem with your question in as much as Buddhism is NOT a theistic religion, So for your question to be valid/make sense you may have to exclude Buddhism from the set you are investigating.

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A religion is a spiritual philosophy/belief that is shared by many people, and often is deeply held. It is considered the best and deepest explanation that various societies have come up with it for the mysteries of life, death and existence, and its core beliefs are taken on faith and are shared by millions.

I simply chose the five largest religions as listed by adherents.org. Why is that unreasonable? I don't see why a religion should have to be theistic to be valid. My question was, what specific beliefs do the world's spritual philosophies (i.e. religions) all share?

You can exclude Buddhism if you wish, but I see no reason for doing so in the context of the original question.