The virgin birth, dying-and-rising god, and December 25th birthdate are all recycled from earlier pagan myths — Mithras, Horus, Dionysus, Osiris. Christianity is just repackaged mythology.

Why people find it persuasive

Parallel-lists circulate widely online and in popular skeptical literature, and the general pattern of ancient religions sharing motifs is real, making wholesale borrowing sound plausible.

Important distinctions

• • Loose thematic resemblance (a god who dies, in some sense) vs. specific claimed parallels that hold up under scrutiny of primary sources.
• • Popular internet 'copycat' lists (Zeitgeist-style) vs. what specialist historians of religion (including non-Christian ones) actually find in the primary evidence.
• • Later syncretism or influence in the opposite direction (pagan cults borrowing from a successful new movement, or later depictions borrowing from Christian ones) vs. early Christian dependence on paganism.
• • Cultural calendar practices (a December date for Christmas) vs. the substantive theological content of the resurrection claim.

Christian response

• • The specific, most commonly repeated parallels do not survive contact with the primary sources: Mithraic texts and iconography (mostly 2nd-4th century AD, later than the Gospels) show no death-and-resurrection narrative for Mithras at all — he is depicted as born from rock (not a virgin) and, per specialists such as the classicist Franz Cumont's successors and more recent scholars like Roger Beck, has no documented dying-and-rising myth resembling the resurrection narrative.
• • Horus is not born of a virgin in Egyptian sources (Isis conceives him after magically reassembling and reanimating Osiris's dismembered body, a considerably less parallel scenario than popularisers suggest), and Osiris's 'resurrection' leaves him ruler of the underworld of the dead, not walking bodily among the living, unlike the Gospels' insistence on physical, this-worldly bodily resurrection (Luke 24:39, 'a ghost does not have flesh and bones as you see that I have').
• • The December 25th date is not claimed by the New Testament itself (no Gospel gives Jesus' birth date) and was fixed by the church considerably later, in the 4th century, likely via calculation from the presumed date of the crucifixion (Sextus Julius Africanus's and later Hippolytus's reasoning) rather than deliberate importation of Sol Invictus's December 25th feast, itself only firmly attested from 274 AD, decades after some Christian sources already discuss the date question — the direction of influence, and even its existence, is disputed among specialists, not settled fact.
• • The chronological direction critics assume is often simply backwards: most alleged 'parallel' mystery-cult texts and artwork post-date the New Testament by one to three centuries, during a period when a rapidly growing, culturally influential new religious movement (Christianity) is at least as likely to have influenced surrounding syncretistic cults' self-presentation as the reverse — a point made by specialist historians of religion including non-Christian scholars like Jonathan Z. Smith, whose Drudgery Divine (1990) is a sustained critique of the popular 'copycat' thesis from within religious studies itself, not Christian apologetics.
• • 1 Corinthians 15's resurrection creed, which Pauline scholars (including skeptical ones like Gerd Lüdemann and Bart Ehrman) date to within roughly five years of the crucifixion via oral formula transmitted to Paul, situates the resurrection claim's origin squarely within a Jewish monotheistic milieu deeply hostile to, not borrowing from, Greco-Roman pagan mythology, which first-century Jews regarded as idolatrous.

Christian counterresponse

That broader observation is fair as a point about shared cultural imagination and the general human intuition that death is not simply final, but it is a considerably weaker and different claim than 'Christianity copied specific pagan myths,' and it does not touch the specific historical case for the resurrection (empty tomb, appearances, radical and rapid transformation of the disciples, the conversion of hostile witnesses like Paul and James) which rests on claimed eyewitness testimony assessed as history, not on comparative mythology.