We (muslims) always say that a muslim will enter Jannah if he has done good deeds and worshipped no one but Allah. Even if a muslims is condemned to Jannaham will eventually enter paradise for being a muslim. How does this go for the jews and Christians? Even though they do not believe in muhammad, they did believe in other major prophets & the books. Do they really need to be a muslim and believe in Muhammad in order to enter Jannah? Will they burn in hell forever or will they enter Jannah too if they have done good deeds? Or is it for a certain amount of time?
If you are referring to the Jews who lived before Islam and believed in One God and the teachings of the Prophet of their time, then are not that different from the Muslims of our Ummah.
They may have sinned like we sin but Allah says He may forgive all sins except if the person died on shirk.
As far as Christians are concerned, please remember that Jesus (Isa) was sent to confirm what was given to the Prophets before him and to also give the glad tidings of a savior after him. Thus he was a Jew and his followers were Jewish.
Many Unitary Christians believe in a single God and inshallah for those who lived before Islam, Allah will have Mercy on them.
Coming to the time after the advent of Islam, unlike the previous Ummahs, Prophet Muhammed was sent as a Prophet & Messenger to all of Mankind & Jinnkind. Thus, they are obligated to analyze what has reached them and using the power of Free Choice that Allah blessed on humans & Jinns decide who they would like to worship.
On the same note, it an obligation on us too to remove the misinformation about Islam and Muslims that many non-muslims receive these days via mainstream media & the political leaders. If only we followed the Quran & Hadiths like the Sahaba did, many would inshallah today convert to Islam by just interacting with us on a day to day basis.