Say someone who has lived a good life, helped people, been a overall good person, is not evil etc. But they are not Muslim or of the Islamic religion, They may be believe in God, may believe in nothing or may not be sure of what they believe in because they simply don't know what to believe in yet, what will happen to them if they die.
Accepting Islam is the single most important criterion that defines how any other deeds beyond that will be perceived. Allah informs us in the Qur'an that there is only one religion, which is Islam, and that anyone who does not follow Islam (even if it is not to follow anything at all) will be among the losers on the Day of Judgment:
وَمَن يَبْتَغِ غَيْرَ الْإِسْلَامِ دِينًا فَلَن يُقْبَلَ مِنْهُ وَهُوَ فِي الْآخِرَةِ مِنَ الْخَاسِرِينَ
And whoever desires other than Islam as religion — never will it be accepted from him, and he, in the Hereafter, will be among the losers.
Even partial belief in Islam does not absolve those who adopt a portion of the religion (let that be good manners or otherwise). Those who believe in some parts of the message of Islam and ignore other parts are considered among the disbelievers:
إِنَّ الَّذِينَ يَكْفُرُونَ بِاللَّهِ وَرُسُلِهِ وَيُرِيدُونَ أَنْ يُفَرِّقُوا بَيْنَ اللَّهِ وَرُسُلِهِ وَيَقُولُونَ نُؤْمِنُ بِبَعْضٍ وَنَكْفُرُ بِبَعْضٍ وَيُرِيدُونَ أَنْ يَتَّخِذُوا بَيْنَ ذَلِكَ سَبِيلًا أُولَئِكَ هُمُ الْكَافِرُونَ حَقًّا وَأَعْتَدْنَا لِلْكَافِرِينَ عَذَابًا مُهِينًا
Indeed, those who disbelieve in Allah and His messengers and wish to discriminate between Allah and His messengers and say, "We believe in some and disbelieve in others," and wish to adopt a way in between — Those are the disbelievers, truly. And We have prepared for the disbelievers a humiliating punishment.
Deeds have three pillars: intention, action, and result. Allah has informed us that the result is His and we as His servants are not accountable for results. However, we are accountable for the actions (what, how, where, and when an action is done, and that all have to be carried through correctly), as we are equally accountable for the intentions being the right ones (see Sahih Al-Bukhari 1/1/1). Accordingly, any deeds from non-Muslims will not have the right intentions (for the sake of Allah). When 'Ā'isha asked the Prophet about Ibn Jud'ān, a virtuous person prior to Islam, he told her his actions were of no avail as they were not aimed at seeking Allah's forgiveness:
عَنْ عَائِشَةَ، قَالَتْ قُلْتُ يَا رَسُولَ اللَّهِ ابْنُ جُدْعَانَ كَانَ فِي الْجَاهِلِيَّةِ يَصِلُ الرَّحِمَ وَيُطْعِمُ الْمِسْكِينَ فَهَلْ ذَاكَ نَافِعُهُ قَالَ: لاَ يَنْفَعُهُ إِنَّهُ لَمْ يَقُلْ يَوْمًا رَبِّ اغْفِرْ لِي خَطِيئَتِي يَوْمَ الدِّينِ
'A'isha reported: I said: "Messenger of Allah, the son of Jud'an established ties of relationship, fed the poor. Would that be of any avail to him?" He said: "It would be of no avail to him as he did not ever say: O my Lord, pardon my sins on the Day of Resurrection."
Ibn Jud'ān never accepted the message of Islam in the first place. But if someone is already a Muslim and apostates, their previous good deeds are rendered worthless (same as when someone is a disbeliever and accepts Islam, their previous bad deeds are erased):
وَلَقَدْ أُوحِيَ إِلَيْكَ وَإِلَى الَّذِينَ مِن قَبْلِكَ لَئِنْ أَشْرَكْتَ لَيَحْبَطَنَّ عَمَلُكَ وَلَتَكُونَنَّ مِنَ الْخَاسِرِينَ
And it was already revealed to you and to those before you that if you should associate [anything] with Allah, your work would surely become worthless, and you would surely be among the losers."
Not only so, but either team is among the greatest losers: They exert lots of effort in this life to do deeds that they would not be rewarded for on the Day of Judgment:
قُلْ هَلْ نُنَبِّئُكُم بِالْأَخْسَرِينَ أَعْمَالًا؟ الَّذِينَ ضَلَّ سَعْيُهُمْ فِي الْحَيَاةِ الدُّنْيَا وَهُمْ يَحْسَبُونَ أَنَّهُمْ يُحْسِنُونَ صُنْعًا أُولَٰئِكَ الَّذِينَ كَفَرُوا بِآيَاتِ رَبِّهِمْ وَلِقَائِهِ فَحَبِطَتْ أَعْمَالُهُمْ فَلَا نُقِيمُ لَهُمْ يَوْمَ الْقِيَامَةِ وَزْنًا ذَٰلِكَ جَزَاؤُهُمْ جَهَنَّمُ بِمَا كَفَرُوا وَاتَّخَذُوا آيَاتِي وَرُسُلِي هُزُوًا
Say, [O Muhammad], "Shall we [believers] inform you of the greatest losers as to [their] deeds? [They are] those whose effort is lost in worldly life, while they think that they are doing well in work." Those are the ones who disbelieve in the verses of their Lord and in [their] meeting Him, so their deeds have become worthless; and We will not assign to them on the Day of Resurrection any importance. That is their recompense — Hell — for what they denied and [because] they took My signs and My messengers in ridicule.
Having said that, if the reason that said non-Muslims did not accept Islam as they have not heard of it, then their matter is with Allah as He wills since He declared that He does not punish those who did not receive a messenger from Him:
مَّنِ اهْتَدَىٰ فَإِنَّمَا يَهْتَدِي لِنَفْسِهِ وَمَن ضَلَّ فَإِنَّمَا يَضِلُّ عَلَيْهَا وَلَا تَزِرُ وَازِرَةٌ وِزْرَ أُخْرَىٰ وَمَا كُنَّا مُعَذِّبِينَ حَتَّىٰ نَبْعَثَ رَسُولًا
Whoever is guided is only guided for [the benefit of] his soul. And whoever errs only errs against it. And no bearer of burdens will bear the burden of another. And never would We punish until We sent a messenger.
Finally, Allah explains to us why those who elect not to accept Islam will have such fate in spite of their good deeds; it is because disbelieving in Allah (this includes partial belief) is a tremendous sin that all other deeds diminish next to, which renders it unforgivable:
إِنَّ اللَّهَ لَا يَغْفِرُ أَن يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَن يَشَاءُ ۚ وَمَن يُشْرِكْ بِاللَّهِ فَقَدِ افْتَرَىٰ إِثْمًا عَظِيمًا
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin.