Armchair (or lawnchair) philosophers often claim that all religions are essentially the same. You may have heard the analogy of the men in the dark feeling different parts of the same elephant. One feels the ear, another the trunk, one a leg. Each would describe the whole elephant very differently while unwittingly touching one single animal. Many say that the various religions are like this: all aspects and outlets of one multi-faceted Truth.
I studied religion at university and had professors from a wide range of religious beliefs or no particular religious belief at all. If there is anyone who believes that religions are very different from one another it is professors of religion. They will be the first to point out the different worldview between major religious groups and the sects within those groups. They tend to shy away from encouraging the practice of comparing one religion to another but are very open to contrasting religions and to pointing out the variety within a religion at the level of, say, a particular village. I never heard one say anything like “All religions are essentially the same.”
Religions deal with the areas which we hold most dear: Truth, a person’s responsibilities before the divine or human realms, the afterlife, and good and evil, among others. If people from different faiths find they agree on something innocuous it is no indication of what they believe about these mountainous topics. The more one learns about the religions of the world the more he or she will see the vast differences even in the things that at first glance may look to be the same.
Allow me to take another direction with this line of thought. What would we think if found a unified system of belief on the great religious topics which originated across several continents, 1500 years, from 40 different authors with very different backgrounds writing a collection of 66 different works? At first glance we would have every reason to doubt; at second glance we would stand amazed and ready to read.