There are many, many parallels throughout the various religious mythologies. As Medievalist (and others) pointed out, virgin births, great floods, journeys to the underworld, and end-times figure into many religious stories. Religions adapt and evolve according to their surroundings and culture.
Study of comparative religion and biblical authorship has brought forth some evidence that Judaism, for instance, was initially a polytheistic religion similar to those of Greece and Rome, or Babylonian, Cannanite, and other Mesopotamian religions. There were multiple gods and various cults that paid tribute to one god in particular. (Cult here has a different meaning than the pop-culture understanding of the word) One of these gods was Yahweh, a war god. Over time, the Yahwist cult grew in popularity and condemned worship of other gods, including the Canaanite gods. This is monolatrist polytheism: acknowledgement of many gods, but worship of one. Monotheism was the eventual result.
Then when the Roman Empire expanded and adopted Christianity, tinges of polytheism from Roman religions crept back in. The idea of the trinity, pantheons of saints, a hierarchy of angels, etc, all have polytheistic origins.
David versus Goliath stories: Homer's Odyssey probably counts.
Journeys to the underworld: Osiris, Dionysus, Hercules, etc. Jesus has the "harrowing of hell" which is a medieval invention (as far as I remember, there's a little scriptural basis for it). Likewise, there's the myth of Orpheus and Eurydice. Orpheus is allowed to take his wife back from the underworld, on the condition he doesn't look back before they both reach the surface. But he does and so he loses his wife. This is rather similar to the story of Lot's wife turning into a pillar of salt.
Death and resurrection: Osiris, Tammuz, Dionysus, etc.
Most ancient religions have stories about, or require, blood sacrifice.
There's also a common feature in religion where its adherents try to connect particular historical figures to divinity, or deem themselves the "chosen people." In Christianity, you have the lineage of Jesus to King David. If I recall correctly, Shinto claims that the line of emperors in Japan all descend from Ameterasu.
(Feel free to correct me if I mixed any of this up)