Mike:
I guess it depends on what you mean by 'prove.' If one starts out as a disinterested onlooker trying to figure out which is the 'correct' religion (and God hasn't told you already), you could:
1) Look at the one with most adherents
2) Look at the one which has changed the least over its history
3) Look at the one which is most recent
4) Look at the one which most coincided with your personal beliefs, desires, fears, or habits
5) Dispassionately compare all with a common yardstick based on the most objective standards you can find
6) Put all the distinct religious sects you can isolate on pieces of paper, put them in a barrel, and draw one out.

As it stands, there are more expressions of belief out there than can possibly be true.

My father's definition of religion is: "The Awe in which we hold our ignorance."