So many things have been achieved through NASA and the space program. I am pretty certain that the picture of the moon walk is a very real one. I can be wary, but it seems pretty silly to question this one event. The shuttle went up and the astronauts came out and of course a moon walk was possible so why not.
Some of the arguments that Neil Armstrong never walked on the moon are some pretty fantastic fiction in and of themselves. But there's an easy way for us to determine that his moon walk did in fact happen, and it comes from the Cold War. Remember, the space race was as much about propaganda as it was about scientific advancement. We were competing with the Soviets, who did in fact track and monitor the United States' moon landings, independently verifying them as having taken place. If anything seems far-fetched, it would have been the very notion that our number one enemy at that time would have passed up the chance to make international headlines exposing NASA as a fraud.