The movie "Zeitgeist" makes the following claims about Mithra:
1. Born of a virgin
2. Born on Dec 25th
3. 12 disciples
4. Performed miracles
5. Dead for 3 days
7. "The Truth"/"The Light" (not visible on the list, but the voice-over says it)
8. Sunday worship"
Other than performing miracles (though they don't correspond to Jesus' miracles - no water into wine, walking on water, or raising the dead), these are all false.
1. Mithra was formed within a mountain, not within a woman (virgin or otherwise)
2. There is no ancient source suggesting Mithra was born on 12/25
3. In the Persian version of the Mithra story, Mithra has a single disciple, Varuna. In the Roman version (which is post-Christian), he has two, Cautes and Cautopatres. Sometimes mythicists show a carving of Mithra slaying a bull while 12 people watch on. There is nothing in the carving suggesting his audience are "disciples", and this carving is post-Christian, so it hardly matters.
4. Yes, he performed miracles, but, again, none similar to Jesus'
5. Dead for three days? The earliest reference to Mithra dying at all dates to the 4th century AD, and is thus post-Christian. And it says nothing about him being dead for 3 days.
6. Resurrected? Not even in post-Christian versions of the story.
7. Called "The Truth" and "The Light"? There is no record of him being called these things
8. Sunday worship? Yes, but only in post-Christian times.