What Does Islam Say About Other Religions?
Question

I have some questions about Islam, could you explain them for me? What does Islam say about people of other religions? Are all non-Muslim people regarded as sinners because they do not follow Allah and Islam? Can any non-Muslim person enter Paradise without following Islam?
Praise be to Allah.The ruling of Islam concerning other religions is that they are all either fabricated and false, or abrogated. 
The fabricated and false religions are those like the ancient Arabian practise of worshipping idols and stones. 
The abrogated religions are those which were taught by the Prophets who came before our Prophet Muhammad (peace and blessings of Allah be upon him). 
They are valid in that their origins are from Allah, but Islam came and took their place, not with regard to basic beliefs such as the existence of God , the angels, Paradise and Hell, for these are matters which all the Messengers have in common, but there are differences between them with regard to ways of worshipping and drawing close to Allah by means of prayer, fasting, pilgrimage, alms, etc. 
The later followers of the Prophets have fallen into deviations of belief and Shirk (associating partners or equals with Allah), but Islam came to point that out and bring people back to the correct belief taught by the earlier Prophets. 
Abu Al-Darda (may Allah be pleased with him) said: `Umar (may Allah be pleased with him) brought some pages of the Torah to the Messenger of Allah (peace and blessings of Allah be upon him) and said, “O Messenger of Allah, these are some pages of the Torah which I took from a brother of mine from (the tribe of) Banu Zurayq.” The expression of the Messenger of Allah (peace and blessings of Allah be upon him) changed, and ‘Abdullah ibn Zayd (may Allah be pleased with him) – who had been shown the Adhan [in a dream] – said, “Has Allah taken away your mind? Do you not see the expression on the face of the Messenger of Allah (peace and blessings of Allah be upon him)?” ‘Umar said, “We are pleased with Allah as our Lord and with Islam as our religion and with Muhammad as our Prophet and with the Quran as our guide.” Then the Messenger of Allah (peace and blessings of Allah be upon him) relaxed, and said, “By the One in Whose Hand is my soul, if Moses (peace be upon him) were to come among you and you were to follow him and leave me, you would have gone far astray. You are my share among the nations and I am your share among the Prophets.” (Narrated by Ahmad, 15437) 
Ibn Hajar said: 
“All the Isnads (chains of narration) of this Hadith are such that they could not be taken as evidence individually, but when taken together they prove that this Hadith is correct.” (Fath Al-Bari, 13/525) 
The evidence for that is the verse in which Allah says (interpretation if the meaning): 
“And whoever seeks a religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers” [Al ‘Imran 3:85]
Imam Al-Tabari (may Allah have mercy on him) said in his commentary on this verse: 
“Allah means that whoever looks for a religion to follow other than Islam, Allah will never accept that from him, ‘and in the Hereafter he will be one of the losers’ meaning, he will be of those who have deprived themselves of their share of the mercy of Allah.” (Tafsir Al-Tabari, 3/339) 
Islam does not regard them (followers of other religions) only as sinners, but as disbelievers who will abide forever in the Fire of Hell, as stated in the verse quoted above. 
The disbeliever will be a loser in Hell, and will not come out of it. It is not possible for a disbeliever to enter Paradise unless he becomes Muslim. Allah says (interpretation of the meaning): 
“Verily, those who reject Our verses (and signs) and treat them with arrogance, for them the gates of heaven will not be opened, and they will not enter Paradise until the camel goes through the eye of the needle (which is impossible). Thus do We recompense the (wicked) criminals.” [Al-A’raf 7:40]
The Prophet (peace and blessings of Allah be upon him) said: “By the One in Whose Hand my soul is, no one of this nation, Jew or Christian, will hear of me and not believe in that with which I have been sent, but he will be one of the people of Hell.” (Narrated by Muslim) 
We ask Allah to guide the seekers of truth from other religions to look into the religion of Islam and its Book, the Quran. May Allah guide them and open their hearts to enter Islam.
For more details, please see the following answers: 14055 , 9607 , 308807 , and 21525 .
And Allah knows best.