Who's right?

I don't understand why it is that everyone believes that their religion is the "True Religion" I was watching a documentary about different religions and Bill Maher was interviewing people of different faiths. He asked them why they believed what they believed and they we're all so committed to there beliefs. I thought to myself  "they all can't be right!" I mean...how does this work? You have the christian who believes that the only way one can get into heaven is to confess Jesus as Lord. Then there are other religions who don't believe that's necessary at all. You have so many religions with different  rules, truth is we are all human beings with a sinful nature, with which we have a really hard time keeping in check. I just find it hard to believe that a loving God who made us human beings with all the imperfections that comes along with this sinful nature of ours would punish us by throwing us in an eternal fire called "Hell." That's like telling a tiger not to act like a tiger, we all know the nature of the beast. How can you punish a tiger for acting on it's natural instinct? Same with us, now as humans we should at least try to exercise some self control, but if the real truth were to be told we're not even able to live without sinful thoughts let alone sinful actions! Tell me.. how this is possible? Religious people are taught to die to themselves, to deny the flesh-in other words fight their human nature. Again telling the tiger not to act like a tiger. I believe that God knows our condition, He knows us-all about us and thank goodness contrary to what many may believe-I believe he sees straight to our hearts and He judges based on our intentions and not so much our actions. I said all this to say we are only human, we'll never be without sin so may I suggest that you simply treat others the way you want to be treated.