To answer the title question...
No. It is not.
Here is my thinking, being a syncretic. Most religions, having stood for centuries are true. If they are not legitimate, they have to spread through the use of violence (as in, convert to my group or I'll kill you, sort of thing; if a religion has to do that, they're a cult).
Hinduism didn't do this, neither has Taoism, Buddhism, Christianity, or Judaism. Most religions stick around because they have an essential truth. So what are these?
- Hinduism - God is many, but the many are actually One. Also kinda the spiritual nature of the everyday (more holidays than anyone). Avatars of some of the deities. Paramatman and Atman, a world soul and individual souls. I kinda barely understand Hinduism.
- Judaism - One of the first monotheistic religions, and also one of the few that pulled away from the use of idols. Before that, many "gods" were actually objects. God is One, and that one is spirit not an object.
- Shinto - Animism. The divine is in everything.
- Taoism - The Yin and Yang. The idea that the universe is in balance. There is also a lesser known teaching about a holograph (that existence is perhaps not real)
- Buddhism - Buddhism is kind of a highbrow religion. I only half-understand it, but the point seems to be a reaction against the Hindu caste system. Buddha also studied under the Jain tradition, so there is alot of self-denial. Buddhism sees the world as a Desire Realm, a sort of illusion where people go through the cycle of rebirth unable to really escape.
- Christianity - Trinity, and Jesus as the savior/messiah. Also grace.
The thing about all of this, is that if we see religion as the concrete, we think we have to commit wholly to the idea of a man named Jesus. That's great and all, but it's not the point. The point? Understanding the spirit of what the religion is trying to say to us. There are a few things beyond the surface.
- First, the Trinity. Aside from the Hindu Triune, there is something different here. Because the Trinity isn't about duty (Creation/Preservation/Destruction), it's about the nature of God. You remember I talked about those other religions, how they believed in either a God, sort of spirits in alot of things, or a sort of avatar? Welp, this is how the Trinity works. We have God (as a deity), we have Jesus (avatar, an incarnate human), and Holy Spirit (Spirit, which empowers souls in a poorly explained way). In other words, just from a sort of half-baked explanation it manages to loosely cover a lot of different religions. I've been a syncretic for awhile, but this ultimately led me back to Christianity proper.
- Second, it is important to recognize that despite all of the fuss Christianity makes about Jesus's name, the name isn't all that important. The TITLE on the other hand, is. Jesus is Savior. And outside of Christianity, there were a ton of Jesus-like figures. People who made sacrifices for others, people who came back from the dead. My personal salvation story doesn't include anyone named Jesus. It does include a girl named Emily, and another named Kira, and others. They helped me straighten my life out, when it deeply sucked and I was considering suicide. Salvation is what is important, not whether the person is named Jesus or Krishna or whatever else.
- Let's make it three points, because I want to emphasize the whole Trinity thing, grace. What is grace? Well, it's the idea that someone cares about you, even in spite of you feeling like a worthless wretch. Now, why is this important outside of Christianity? Alright then, think about someone who has managed to screw their life up through terrible deeds. Karma (what Jews call The Law) would decide that they will probably have a sucky path to new life. At some point, the whole thing winds up feeling hopeless. The point is, when you feel like maybe things aren't quite as bad as they seem, suddenly you wind up trying to turn things around. I'm pretty bad at explaining this, but the point is you fare better because you understand that someone looks up for you regardless. Now, this is only half of the equation, but in addition to you improving your life as a result of goodwill and their believing in you, the idea of grace is that you are probably already okay. You can't really earn grace, so in essence, the more worried about following the law you are, the more likely you will screw up. This is kind of a hard pill to swallow for believers in karma though.
If you want to get a sense of what Christianity can accomplish in one who isn't a Christian, read Deepak Chopra
Life After Death: The Burden of Proof. He seamlessly blends the two faiths of Hindu/Christian in a way that I found myself liking even when I had no understanding of some of the Hindu metaphors.
Christianity is important to non-Christians, but the emphasis is taken away from the specific trappings, and more as part of the general idea of what salvation and grace mean.