Religion stems from at its most basic, a fear of the unknown. people (I hate to say create but it's really the only word that seems to fit) religions and myths to attempt to explain the questions science is either unable to answer at the time.
most religions have a strong tie to the idea of an afterlife or a life after death. this tends to be a primary thread between them.
However the most common tie between religions is the belief that the world came into being as a result of a being or beings or occured spontaniously alongside said beings.
An interesting thing to look at would also be flood myths. take a look: [link]
There is one deity. That omnipotence can be described as a single corporeal being, multiple corporeal beings, male, female, genderless, all genders, conceptual, a grouping of emotions, a person, or really any other way that a deity may be conceptualized. The names are changed, multiples are rolled into one, one is broken into multiples, etc.
Then the religion uses that deity to describe a general moral and social code that more or less creates a social structure motivating followers to be mindful of others and generally not be selfish pricks that would lead to the downfall of society, along with some localized rules regarding specific cultural and environmental traits (shellfish, beef, pork taboos, etc).
The rest is merely explanation for things that science cannot yet explain and elude most other forms of philosophy.
But more or less the message is the same, the deity is the same, but the names and stories are changed to fit a local culture.
If you think Zeus and Thor fall into the "nice, fuzzy, personal, omnipotent sky daddy" category, you're badly misinformed.
"Christianity is generally a very interpersonal religion, because it's all about having a relationship with Jesus" No, that's not what Christianity is. That's what one branch of Christianity is. One aspect. The very extreme Jesus fixation that happens in some branches simply isn't practised in others. For instance, when I got my confirmation according with the tradition of Danish protestants, the priest did talk about Jesus but much more about God directly.
I don't think most people act like all religions are the same.
I do think lots of ignorant people spout off about religion in badly created OPs like this one.
All religions might be different in some way or another, but they're still inherently the same. According to the ancient Romans, what made a religion an actual religion was the worship of a deity. Didn't have to be polytheistic, either, you just had to have a deity to worship. That's what made it a religion and not a sect or form of philosophy. And a lot of people still define religion in the same way today. When I think of all the different religions I've learned about over the years, they all share one thing in common in my opinion and that is the worship of a deity or deities. The means of worship vary from culture to culture, but it's still worship. That's why I personally act as if all religions are inherently the same. Now if you want to talk about philosophy, that's a whole different ballgame.