Zeitgeist. (Note: The movie covers more ground than merely making allegations against the uniqueness of Christianity. I will not presently be mentioning anything other than the material that is relevant to Christianity specifically.)
I won't try to reinvent the wheel. Mark Foreman has a very satisfactory first-pass Christian reply. His article is printed as "Challenging the Zeitgeist Movie: Parallelomania on Steriods" in the volume entitled: Come Let us Reason, Paul Copan and William Lane Craig, Eds. (B&H: Nashville, TN, 2012), pp. 169-185. I will herein summarize a few of (what I take to be) Foreman's most salient points.
As a sort of preliminary, however, I will note that this image has a difficulty that is common to (what I have elsewhere called) "internet polemics" in general - namely, there are little to no sources cited (in this case, no sources cited at all).
(Since it seems likely to me that the single source for this picture is the Zeitgeist movie itself, the image content is only as good as the Zeitgeist sources. And these are questionable, at best. For all of its voluminous citations, the movie relies heavily on a handful of texts, marginal scholars, and several dated works. I myself am open to the possibility that criticisms of, for example, James Frazer's Golden Bough can be at least partially rebutted and his work (to take just one instance) made available for use as a credible source. But this sort of task - of addressing criticisms of Frazer - must actually be carried out. And the necessary work simply has not been done.)
By my lights, Foreman's main points are as follows.
Firstly, responsible "comparative religious study" is carried out by noting contrasts as well as comparisons. Typically, however, in Zeitgeist-style presentations, contrasts between Jesus and the various pagan deities are seldom (if ever) acknowledged. Skipping an honest appraisal of differences tends to give the impression either that there simply are no noteworthy differences (which is simply false) or that the differences are less substantial than, or outweighed by, the similarities (which may be true or false but which can hardly be seriously decided by only looking at similarities).
For example, Attis is a Phrygian deity (also cropping up in Greek mythology) who died (in some versions of his story) through bleeding to death as the result of castration. It may be that, in some versions, Attis' castrated and bleeding body was affixed to some sort of tree - usually a pine. But in other versions, it appears that he merely dies proximate to a pine - perhaps with his blood "fertilizing" the tree (similar to Zeus' fertilization of ground that produced the pomegranate). In any case, the point is that in the myth of Attis there is a distinct focus on castration that is altogether absent in the biblical texts relating the story of Jesus. And this difference seems important enough to mention.
Secondly, in a serious comparative religious enterprise, the comparisons that are made should arise "organically." That is, roughly speaking, they should not be "artificial" or forced comparisons. However, in Zeitgeist-style presentations, at least two difficulties arise at this point. Number one, a comparison can fail to be clearly "organic" (in the relevant sense) if the point of comparison is only obvious once a myth with differing versions has had one version carefully selected in order to make the comparison obvious, when it would not have been obvious otherwise.
Take a case. Let's consider Attis again. There are numerous versions of the Attis myth, as has been stated. In some versions, Attis is said to have castrated himself and subsequently bleeds to death (this may correspond to various goddess cults where male priests ostensibly castrated themselves in acts of worship). In other versions, he is castrated by a rival king (which rivalry may correspond to the sacred king-tanist duality in killing of the divine king type rituals). Sometimes, Attis is said to have been castrated by a wild animal - chiefly, a boar. And, as has been mentioned, these castrations are linked to the pine tree in various ways - for example, Attis may be castrated and die under or near the tree, or he may be castrated and then die on or in the tree, or he may be placed on or in the tree and then castrated, etc. But which version shall we favor? It's not at all clear - at least to me - that a version of the Attis myth where, say, Attis castrates himself and perishes on the floor of a forest, is any sort of Jesus parallel - let alone an obvious parallel. In Zeitgeist-style presentations, the favored version of a myth is decided in advance by the agenda of the film. Since the point of a Zeitgeist-style presentation is to suggest mythological antecedents for Jesus, it is apparent that the favored version of the Attis myth (or any other myth) will be that version that seems the closest to the story of Jesus. Foreman puts it this way: "These writers [such as the Zeitgeist authors] seem to use the life of Jesus as a guide for how to connect the dots for the life of [a pagan god, e.g. Attis or Horus] and then proclaim that the story of Jesus is based on [that god] - when actually [in terms of the direction of comparison] it is the other way around!" (p. 182)
Number two, the comparisons can fail to be "organic" if the comparison is anachronistically or ectopically labeled with distinctly Christian terms. Foreman calls this "the terminological fallacy," by which he means that "events in the lives of mythical gods...are expressed using Christian terminology in order subtly [or not so subtly] to manipulate viewers into accepting that the same events in the life of Jesus also happened in the lives of mythical gods."
Foreman specifically mentions the following illustrations of this phenomenon. "We are told...that Horus, Krishna, Dionysus, and others were 'baptized,' 'born of a virgin,' 'crucified,' and 'resurrected'... . Examples of such locutions, however, involve assertions with no evidence, are ripped out of their Christian context, or are obtained from post-first century [and hence post-early-Christian] sources" (p. 177).
Just take the case of "baptism." Both the baptism of John the Baptist (which Jesus underwent) and the distinctly Christian baptisms (which function as an initiatory rite into Christianity), are theologically "thick" notions. That is, they arguably contain numerous, discrete concepts. Now it would indeed be quite remarkable if a comparison of Christian baptism (in either or both of the relevant senses) with, say, something in the life of Horus, had substantive points of contact with some weighted sum of the various concepts in the "thick" conception. But, such a "thick" conception is usually set aside in favor of a "thin" conception whereby "baptism" is evacuated of most (if not all) of its distinctly Christian constitutive concepts, and "baptism" is reduced to something very common, such as "being in water" (or something). But comparisons employing such "thin" concepts are arguably entirely unremarkable. If "baptism" merely means the very "thin" notion of "being in water," then, of course, numerous pagan gods will be "comparable" to Jesus in this sense, for it is very common for persons to be in water. As I said, "thicker" notions of baptism will get increasingly more interesting - the "thicker" they become. But we need to have a careful explanation of the full concept of "baptism" that is being compared in order to gauge the level of interest that the comparison has. But, Zeitgeist-style presentations typically include nothing remotely approaching "a careful explanation of the full concept of 'baptism' that is being compared". Usually, Zeitgeist-style presentations appear to have a very "thin" concept of "baptism" and use the word "baptism" without qualification arguably in order to obscure this thinness.
As a quick follow-up, the case of Mithraism yields an example of what Foreman termed evidence "obtained from post-first century [and hence post-early-Christian] sources" (Ibid.). For although Mithraism predates the second century, all of the extant evidence for Mithraic beliefs and practices dates from no earlier than the second century. The earliest descriptions of Mithraism that we possess date from an era that comes after the inception of Christianity. Hence, even apparent similarities between Mithraism and Christianity can be explained in one of (at least) three different ways: (1) coincidence, (2) Christianity consciously borrowing from Mithraism, or (3) Mithraism concsiously borrowing from Christianity. Although option #1 is arguably rightly disfavored and set aside, somehow the third option is seldom even mentioned, let alone seriously discussed. But, prima facie, it might seem like the best option. Here's one reason: Mithraism was a famously syncretistic mystery cult; whereas, Christianity was scrupulously exclusivistic (many Christians died, in fact, rather than incorporate foreign ideas into their belief system). Therefore, given a deliberate policy of syncretism, Mithraism is, in might be suspected (antecedently) highly likely to have modified (at least the presentation, and possibly the deeper significance of) many of its beliefs and practices as a result of historical contact with Christianity.
Thirdly, and lastly for present purposes, Foreman makes the point that much of what passes as an insight into legitimate comparative religion, is merely a glossy and lengthy instance of the logical fallacy known as post hoc, ergo propter hoc - that is, the fallacy that starts with a premise that says B happened after A and then automatically tries to conclude, from time sequence alone, that B happened BECAUSE OF A.
A sort of textbook example of this would be something like the following: "I had a cold. I took some over-the-counter cold relief formula and then my cold was gone the next morning. Therefore, my cold was gone the next morning BECAUSE I took the cold relief formula the previous night." But, the conclusion does not automatically follow from the stated premise alone, because it is entirely possible (to consider just one example) that the cold had nearly "run its course" and would have been "gone the next morning" even if I had not consumed the cold relief formula when I did.
In a similar way, the basic structure of a number of Zeitgeist style arguments seems merely to be this: Jesus came after such-and-such god. Therefore, Jesus is based on such-and-such god. But, in this form, the argument seems to commit the "after this, therefore because of this" fallacy.
As a final word Foreman points out, following Hugo Rahner, that insofar as "humans are religious beings" (as Proverbial wisdom often asserts and which Christianity seems explicitly to hold), we should expect that the myriad forms of human religion should have numerous points of similarity and overlap - symbolically, doxastically, and practically. This really should not surprise reflective observers. Of course, substantial comparisons can be interesting. But if they are to amount to more than curious anecdotes, such comparisons will have to be meticulously drawn and contrasts will have to be soberly evaluated. In some cases, two hour presentations fail to be sufficiently meticulous or sober. A fortiori, we should be very suspicious about hastily put together text-images.