@Watchman: "abandoned child motif"

That one even reached Japan in the form of the Momotaro (Peach Boy) story. A baby is found inside a giant peach floating down a river.

Well put.

I'd bet stories like these can die down and live as local legends for centuries in a society before being revived as new revelation again and again.

Most of the parallelisms drawn are pretty strained. OP says that Gilgamesh was half human and half divine (half god) but so many demigods did have this characteristic.

1. "The resurrection: Gilgamesh precedes jesus by 2700+ years" - Your 'source' fails to quote the actual 'Epic of Gilgamesh', whereas I did.
2. "Crucified "saviors" that precede jesus: Here is Graves' main list, arranged chronologically" - Uh yeah. Several problems found:
Graves often does not distinguish his opinions and theories from what his sources and evidence actually state.
Graves often omits important sources and evidence.
Graves often mistreats in a biased way the sources he does use.
Graves occasionally relies on suspect sources.
Graves does little or no source analysis or formal textual criticism.
Graves' conclusions and theories often far exceed what the evidence justifies, and he treats both speculations and sound theories as of equal value.

And again I posted PRIMARY sources. I found a PDF of the book done by Grave's and I couldn't find a single source, only quotation marks around certain words, with no reference or citation.

3. "The rising from the dead as gods:"
a. Tammuz dies yearly, Jesus died only once. Tammuz also goes to the underworld, Jesus has never been.
b. Osirus doesn't really come back from the dead; the body his destroyed, but his (I guess it would be called) 'conscious' lives on as a member of the shadowy underworld.
c. The best account we have of Dionysus coming back, which reads "Dionysus (was) torn in pieces by them, and his remains being afterwards put together again, he returned as it were once more to life, and ascended into heaven". There is a problem though, this was written by CHURCH FATHER Origen, roughly 2-and-a-half centuries after Jesus.
d. Edwin M. Yamauchi, professor of history at Miami University, Ohio, in his article Easter: Myth, Hallucination, or History states, “P. Lambrechts has shown that there is no trace of a resurrection in the early texts or pictorial representations of Adonis; the four texts that speak of his resurrection are quite late, dating from the second to the fourth centuries A.D. "A Zeal for God Not According to Knowledge" writes that "no sources refer to the second century, pictorial or literary, mention Adonis's resurrection."
e. Attis: AJM Wedderburn writes: "At least down to the mid second century C.E the rites of Attis were ones of mourning, unmixed with any joy at resurrection...Wagner follows Nilsson in seeing the first mention of a resurrection of Attis in the Fourth Century C.E." In 'Mother of the Gods: From Cybele to the Virgin Mary', "It is therefore between the third and fourth centuries, and most likely under Christian influence, that the ideology of Attis' resurrection was developed"

4. "Born of virgins myths:" - Only a couple of these are virgin births. Please tell me if I missed any.
a. https://en.wikipedia.org/wiki/Horus: "Horus was born to the goddess Isis after she retrieved all the dismembered body parts of her murdered husband Osiris, except his penis, which was thrown into the Nile and eaten by a catfish,[7][8] or sometimes depicted as instead by a crab, and according to Plutarch's account used her magic powers to resurrect Osiris and fashion a golden phallus[9] to conceive her son (older Egyptian accounts have the penis of Osiris surviving)." - Not virgin birth. (But gross af)
b. Dionysus: Daniel B. Wallace writes,"The virgin birth of the pagan god Dionysus is attested only in post-Christian sources...several centuries after Christ." (Reinventing Jesus, p. 242).
c. Mithra: Despite the claims of obvious and profound parallels between Christianity and Mithraism, when one looks at the evidence an entirely different picture emerges. First, Mithra was not thought of as virgin born in the most ancient myths; rather, he arose spontaneously from a rock in a cave." (Cited in Reinventing Jesus, p. 242). Lee Strobel adds, "Unless the rock is considered a virgin, this parallel with Jesus evaporates." (The Case for the Real Jesus, p. 171).
d. Vishnu (and a tiny bit of Hercules): Charlie Campbell says, "The Zeitgeist movie says that Krishna, a supposed incarnation of the Hindu god Vishnu, was born of a virgin. Edwin Yamauchi says, "That's not accurate. Krishna was born to a mother who already had seven previous sons, as even his followers concede." (Quoted by Lee Strobel in The Case for the Real Jesus, p. 182).Dr. William Lane Craig says, "The alleged pagan parallels to this story [the story of the Virgin Birth, or, more accurately, Jesus' virginal conception] concern tales of gods' assuming bodily form and having sexual intercourse with human females to sire divine-human progeny (like Hercules). As such these stories are exactly the opposite of the Gospel story of Mary's conceiving Jesus apart from any sexual relations. The Gospel stories of Jesus' virginal conception are, in fact, without parallel in the ancient Near East." (From online article by William Craig, "Jesus and Pagan Mythology")

Try this site: http://www.alwaysbeready.com/zeitgeist-the-movie

5. "The flood myth:" - Basically, all the 'sources we have', is the 'Epic of Gilgamesh' and Genesis. Both talk of a colossal flood. I believe that they both talk of the same flood, but the Epic was written close to after it was finished, but Genesis was written quite a bit after.