If one of the many thousands of religions that have existed were uniquely true, wouldn’t it be pretty obvious? Wouldn’t its followers be noticeably different from all of the other people on the planet,, since only they would be connected to the world’s greatest truth?
You would expect to find them noticeably more peaceable than followers of other faiths, less violent. They wouldn’t be committing, or have a history of committing, torture; nor ordering murder, nor inciting warfare. I’d predict they’d be more unselfish, thoughtful, and visibly more loving than the rest of us. Because they were in touch with the one true God(s), they would be calmer, less fearful. They should be happier. However they might look, they would be distinctively different from us.
Some Eastern philosophies show just those tendencies, or at least they did before human followers turned founders into gods and philosophies into religions. But at a minimum we can say that Christianity doesn’t make the cut. Christianity is no worse than the other options – it just isn’t any better either. There is simply nothing special or unusual about Christians that would suggest that they are the (only) ones on the right track.