Is Spidey agnostic?
Is Spidey Catholic?
Is Spidey Jewish?
I'd get these kinds of questions a lot.
My answer is: Spidey is universal. "Anyone can wear the mask."
To nail down Spidey's religion (or to keep bringing it up) makes him less universal.
A lot of Spidey writers from Stan to Bendis to myself have been Jewish. There are Jewish mannerisms and phrases thrown in there from time to time. But the SAME can be said of other Spider writers of other religions over the 50+ years of Spider-Man stories. Everything's valid.
If you want to get technical, there are (very rare) canonical stories that clearly state that both (Uncle) Ben Parker and (Aunt) May Reilly are Irish Americans. And we've seen Peter celebrate X-Mas.
But looking at it that way (to me) misses the point.
Spidey is universal.
To bring up Spidey's religion isn't necessary.
You should be able to see yourself reflected in Spidey. Everyone should.
Spidey's REAL religion can be summed up in one phrase:
"With Great Power There Must Also Come Great Responsibility."
'Nuff Said.