G-d tells us how he wants us to live. You either choose to follow or you don't. G-d isn't going to burn you for eternity just because you didn't know some dude that lived thousands of years ago. That's absurd. But what he Did do is have 3 million witness to mt Sinai and the giving of the Torah (5 books of Moses) by G-d so people know it's divine. However the adding to it by people makes the new version Not divine. Since the Torah says its for eternity, and to never add or change it. There could be some kind of cleansing before entering heaven, perhaps more so for the wicked people. But we can all go. People of every Faith.
Also, why only Christianity and Judaism? Why not Mormonism or Islam? Or, by extension, Buddhists, who are generally good people, Humanists, who are generally good people, or any other good person? Why should one be punished, FOR EVER IN THE MOST PAINFUL WAY POSSIBLE, for being good but not believing in something they have no reason to believe in? Once the middle area here is so grey, this philosophical question falls down.
Also, you can't go somewhere which does not exist.
Some factions of Jewish people do not believe in Heaven and Hell, but in Sheol, the abyss for all who are dead and/or Gan Eden (The Garden of Eden) where the dead will be welcomed to (as a paradise) in the afterlife.
(I know this from personal beliefs, but if you'd like a source http://www.myjewishlearning.com/beliefs/Theology/Afterlife_and_Messiah/Life_After_Death/Heaven_and_Hell.shtml )
Matthew 7:21-23 (NASB)
21 “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter. 22 Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ 23 And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness.’