This is actually a huge topic of debate in Islam. On one hand the Quran tells us that anyone who dies without accepting after they've heard the words of Allah will suffer. And yet it also says that anyone who associates partners with Allah or worships a God other than Allah will be of the Losers (those in hell). It is generally accepted by most scholars that people who do not know of Islam are to be judged on their observation of the revelation they did know (among the many messengers sent to all nations before Islam (ie most consider these all the Monotheistic religions and even the religions which have a supreme God and those beneath him))... Now what scholars and others don't agree on is what constitutes "knowing" or "hearing" of Islam. If I run Into a crowd and yell "La Ilaha Il-Allah, Muhammadur Rasulullah" does anyone know what I mean. Even if I say it in English "There is No God worthy of worship But Allah, And Mouhammed is his Messenger" Have I really explained to those people anything? If People are told constantly that Islam is a Religion, but all they know is what they see on Fox News, is there any reason for them to believe it is the truth?
All in All it is up to God in the end...