It is not a question of "believe" anymore, but sorting out the facts and getting to the truth, which is out there. Most people ignore the facts as it way beyond they paradigm or what they have been accustomed to.
There are videos of serious people on my site, like astronauts for example. They are not crazy 'conspiracy nuts', but very serious people. There are ex-military, pilots and ex-government officials from several countries, including ex-defense minister of Canada speaking out as well as well documented UFO encounters by few US presidents. Past Governor of New Mexico admits there was something unexplained during "phoenix lights" night event, which is still undisclosed. Few countries already disclosed UFo information, which media is not reporting about. There was good Larry King shows about the whole topic few years back, can find it on my site or Youtube.
Area 51 is the most famous incident with many old people giving testimonials now.
The US government hides the truth from its citizens and is involved in mass conspiracy hiding extraterrestrial presence. I guess because of the consequences it could bring while revealing such contact, but possibly they may want to extract alien technology for military porpoise by re-engineering "flying saucers" to get advantage over the enemy.