The question is; who built the foundation of our belief and is it possible for something or someone to prove to you that their foundation is the best one to build on?
The reasons we believe or don't believe in something stems from our ancestral tree, where our foundation takes root. Your parent(s) shape who you are (and their parents shaped who they were, and so on), like it or not, and that molding, the circumstances surrounding that molding and all sorts of outside influences guide the formation of your essential beliefs. More often than not our beliefs are emotional rather than logical.
Belief is not proof. Belief is faith. If you somehow had the ability to travel back in time and took me back to the beginning of the world and there, with my very own eyes, I witnessed the "big bang" (the cosmic sneeze, the galactic lightning, the interstellar rabbit from a hat), proving the development of the world; even with my personal conversion I still wouldn't be able to convince others to alter their belief based on my witnessing. Now imagine God appears to an atheist or skeptic, saying "Here I am, you wanted proof that I exist, well; here ya go. Watch me turn the grass blue *snap* — it's blue". You wouldn't be able to convince others that what you saw was real. You wouldn't be able to prove to them that their beliefs ought to change, despite fact or evidence. Even after all the video, personal witnesses and documentation there are more than a few who believe the moon landings were a hoax propogated by the government. Evidence doesn't produce faith.
Your beliefs can (and will) change and evolve, but it isn't because someone has proved to you that it ought to be so, its because your personally and emotionally moved your foundation to another location. The evidence for your beliefs come after your faith; not before.
This is Dennis Prager doing a phenominal job of explaining what I feebly attempted to above.